Order Number: MPC8240TS/D
Rev.1, 7/1999
© Motorola, Inc., 1999. All rights reserved.
ª
Advance Infor mation
MPC8240 Integrated Processor Technical
Summary
This document provides an overview of the MPC8240 PowerPCª integrated processor for high-
performance embedded systems. The MPC8240 is a cost-effective, general-purpose integrated processor for
applications using PCI in networking infrastructure, telecommunications, and other embedded markets. It
can be used for control processing in applications such as network routers and switches, mass storage
subsystems, network appliances, and print and imaging systems.
For errata or revisions of this document, refer to the website at http://www.mot.com/powerpc.
1.1 MPC8240 Integrated Processor Overview
The MPC8240 integrated processor is comprised of a peripheral logic block and a 32-bit superscalar
PowerPC processor core, as shown in Figure 1-1.
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MPC8240 Integrated Processor Technical Summary
MPC8240 Integrated Processor Overview
Figure 1-1. MPC8240 Integrated Processor Functional Block Diagram
The peripheral logic integrates a PCI bridge, memory controller, DMA controller, EPIC interrupt controller,
a message unit (and I
2
O controller), and an I
2
C controller. The processor core is a full-featured, high-
performance processor with ßoating-point support, memory management, 16-Kbyte instruction cache, 16-
Peripheral Logic
Instruction Unit
System Integer Load/Store Floating-
Address
Translator
DLL
Fanout
Buffers
PCI
Arbiter
Data Instruction
16-Kbyte
16-Kbyte
Message
Unit
(with I2O)
I2C
Controller
DMA
Controller
Interrupt
Controller
EPIC
/Timers
PCI Bus
Interface Unit
Memory
Controller
Data Path
ECC Controller
Central
Control
Unit
32-Bit OSC InFive
Request/Grant
Pairs
I2C
5 IRQs/
Processor Core Block
Peripheral Logic Block
Processor
PLL
(64 bit) Two-instruction Fetch
(64-bit) Two-instruction Dispatch
Peripheral Logic
PLL
SDRAM Clocks
PCI Clock In
PCI Bus Clocks
Data (64 bit)
Address Data Bus
(32- or 64-bit)
DRAM/SDRAM/
Address/Control
64 bit
PCI Interface
16 Serial
Interrupts
Branch
Processing
Unit
(BPU)
MPC8240
Bus
Configuration
Registers
Register
Unit
(SRU)
Unit
(IU)
Unit
(LSU)
Point
Unit
(FPU)
(32 bit)
Data
Cache
Instruction
Cache
MMUMMU
Additional features:
¥ JTAG/COP Interface
¥ Power Management
with 8-bit Parity
or ECC
SDRAM Sync Out
SDRAM Sync In
ROM/Flash/Port X
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MPC8240 Integrated Processor Technical Summary
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MPC8240 Integrated Processor Overview
Kbyte data cache, and power management features. The integration reduces the overall packaging
requirements and the number of discrete devices required for an embedded system.
The MPC8240 contains an internal peripheral logic bus that interfaces the processor core to the peripheral
logic. The core can operate at a variety of frequencies, allowing the designer to trade off performance for
power consumption. The processor core is clocked from a separate PLL, which is referenced to the
peripheral logic PLL. This allows the microprocessor and the peripheral logic block to operate at different
frequencies, while maintaining a synchronous bus interface. The interface uses a 64- or 32-bit data bus
(depending on memory data bus width) and a 32-bit address bus along with control signals that enable the
interface between the processor and peripheral logic to be optimized for performance. PCI accesses to the
MPC8240Õs memory space are passed to the processor bus for snooping when snoop mode is enabled.
The processor core and peripheral logic are general-purpose in order to serve a variety of embedded
applications. The MPC8240 can be used as either a PCI host or PCI agent controller.
1.1.1 MPC8240 Integrated Processor Features
Major features of the MPC8240 are as follows:
¥ Peripheral logic
Ñ Memory interface
Ð Programmable timing supporting either FPM DRAM, EDO DRAM or SDRAM
Ð High-bandwidth bus (32/64-bit data bus) to DRAM
Ð Supports one to eight banks of 4-, 16-, 64-, or 128-Mbit memory devices
Ð Supports 1-Mbyte to 1-Gbyte DRAM memory
Ð Contiguous memory mapping
Ð 16 Mbytes of ROM space
Ð 8-, 32-, or 64-bit ROM
Ð Write buffering for PCI and processor accesses
Ð Supports normal parity, read-modify-write (RMW), or ECC
Ð SDRAM data-path buffer
Ð Low voltage TTL logic (LVTTL)
Ð Port X: 8-, 32-, or 64-bit general-purpose I/O port using ROM controller interface with
address strobe
Ñ 32-bit PCI interface operating up to 66 MHz
Ð PCI 2.1-compatible
Ð PCI 5.0-V tolerance
Ð Support for PCI locked accesses to memory
Ð Support for accesses to all PCI address spaces
Ð Selectable big- or little-endian operation
Ð Store gathering of processor-to-PCI write and PCI-to-memory write accesses
Ð Memory prefetching of PCI read accesses
Ð Selectable hardware-enforced coherency
Ð PCI bus arbitration unit (Þve request/grant pairs)
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MPC8240 Integrated Processor Technical Summary
MPC8240 Integrated Processor Overview
Ñ PCI agent mode capability
Ð Address translation unit
Ð Internal conÞguration registers accessible from PCI
Ñ Two-channel integrated DMA controller
Ð Supports direct mode or chaining mode (automatic linking of DMA transfers)
Ð Supports scatter gatheringÑread or write discontinuous memory
Ð Interrupt on completed segment, chain, and error
Ð Local-to-local memory
Ð PCI-to-PCI memory
Ð PCI-to-local memory
Ð Local-to-PCI memory
Ñ Message unit
Ð Two doorbell registers
Ð Inbound and outbound messaging registers
ÐI
2
O message controller
ÑI
2
C controller with full master/slave support
Ñ Embedded programmable interrupt controller (EPIC)
Ð Five hardware interrupts (IRQs) or 16 serial interrupts
Ð Four programmable timers
Ñ Integrated PCI bus and SDRAM clock generation
Ñ Programmable memory and PCI bus output drivers
Ñ Debug features
Ð Memory attribute and PCI attribute signals
Ð Debug address signals
Ð MIV signal: Marks valid address and data bus cycles on the memory bus.
Ð Error injection/capture on data path
Ð IEEE 1149.1 (JTAG)/test interface
¥ Processor core
Ñ High-performance, superscalar processor core
Ñ Integer unit (IU), ßoating-point unit (FPU) (user enabled or disabled), load/store unit (LSU),
system register unit (SRU), and a branch processing unit (BPU)
Ñ 16-Kbyte instruction cache
Ñ 16-Kbyte data cache
Ñ Lockable L1 cacheÑentire cache or on a per-way basis
Ñ Dynamic power management
1.1.2 MPC8240 Integrated Processor Applications
The MPC8240 can be used for control processing in applications such as routers, switches, multi-channel
modems, network storage, image display systems, enterprise I/O processor, Internet access device (IAD),
disk controller for RAID systems, and copier/printer board control. Figure 1-2 shows the MPC8240 in the
role of host processor.
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MPC8240 Integrated Processor Technical Summary
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MPC8240 Integrated Processor Overview
Figure 1-2. System Using an Integrated MPC8240 as a Host Processor
Figure 1-3 shows the MPC8240 in a distributed I/O processor application.
PCI Bus
Peripheral 1 Peripheral 2 PCI-to-PCI
Bridge
Peripheral 3
Main Memory:
DRAM, EDO,
SDRAM
Peripheral
I2C
EPIC
ROM
CTRL
Data
Port X
Processor Core
MPC8240
DMA
MU(I2O)
PCI Bus
Logic
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MPC8240 Integrated Processor Technical Summary
MPC8240 Integrated Processor Overview
Figure 1-3. Embedded System Using an MPC8240 as a Distributed Processor
Figure 1-4 shows the MPC8240 as a peripheral processing device. The PCI-to-PCI bridge shown could be
of the PCI type 0 variety. The MPC8240 would not be part of the system conÞguration map. This
conÞguration is useful in applications such as RAID controllers, where the I/O devices shown are SCSI
controllers, or multi-port network controllers where the devices shown are Ethernet controllers.
PCI Bus
Peripheral Peripheral PCI-to-PCI
Bridge
PCI Bus
System
Peripheral 2
Main Memory:
DRAM, EDO,
SDRAM
ROM
CTRL
Data
Port X
Processor Core
MPC8240
3 I/O
Controller
1
Host Bridge
Host Processor
Host Memory
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MPC8240 Integrated Processor Technical Summary
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Processor Core Overview
.
Figure 1-4. Embedded System Using an MPC8240 as a Peripheral Processor
1.2 Processor Core Overview
The MPC8240 contains an embedded version of the PowerPC 603eª processor. For detailed information
regarding the processor refer to the following:
¥
MPC603e & EC603e UserÕs Manual
(Those chapters that describe the programming model, cache
model, memory management model, exception model, and instruction timing)
¥ PowerPC Microprocessor Family: The Programming Environments for 32-Bit Microprocessors
This section is an overview of the processor core, provides a block diagram showing the major functional
units, and describes brießy how those units interact. For more information, refer to Chapter 2, ÒPowerPC
Processor Core,Ó in the
MPC8240 UserÕs Manual
.
The processor core is a low-power implementation of the PowerPC microprocessor family of reduced
instruction set computing (RISC) microprocessors. The processor core implements the 32-bit portion of the
PowerPC architecture, which provides 32-bit effective addresses, integer data types of 8, 16, and 32 bits,
and ßoating-point data types of 32 and 64 bits.
The processor core is a superscalar processor that can issue and retire as many as three instructions per
clock. Instructions can execute out of order for increased performance; however, the processor core makes
completion appear sequential.
Host Bridge
Host Processor
Host Memory
Main Memory:
DRAM, EDO,
SDRAM
ROM
CTRL
Data
Port X
Processor Core
MPC8240
PCI Bus
Peripheral Peripheral System
Peripheral 2
PCI-to-PCI
Bridge
Local PCI bus
I/O I/O
DeviceDevice
1 3 I/O
Controller
Peripheral
I2C
EPIC
DMA
MU(I2O)
Logic
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MPC8240 Integrated Processor Technical Summary
Processor Core Overview
The processor core integrates Þve execution unitsÑan integer unit (IU), a ßoating-point unit (FPU), a
branch processing unit (BPU), a load/store unit (LSU), and a system register unit (SRU). The ability to
execute Þve instructions in parallel and the use of simple instructions with rapid execution times yield high
efÞciency and throughput. Most integer instructions execute in one clock cycle. On the processor core, the
FPU is pipelined so a single-precision multiply-add instruction can be issued and completed every clock
cycle.
The processor core supports integer data types of 8, 16, and 32 bits, and ßoating-point data types of 32 and
64 bits.
The processor core provides independent on-chip, 16-Kbyte, four-way set-associative, physically addressed
caches for instructions and data and on-chip instruction and data memory management units (MMUs). The
MMUs contain 64-entry, two-way set-associative, data and instruction translation lookaside buffers (DTLB
and ITLB) that provide support for demand-paged virtual memory address translation and variable-sized
block translation. The TLBs and caches use a least recently used (LRU) replacement algorithm. The
processor also supports block address translation through the use of two independent instruction and data
block address translation (IBAT and DBAT) arrays of four entries each. Effective addresses are compared
simultaneously with all four entries in the BAT array during block translation. In accordance with the
PowerPC architecture, if an effective address hits in both the TLB and BAT array, the BAT translation takes
priority.
As an added feature to the processor core, the MPC8240 can lock the contents of one to three ways in the
instruction and data cache (or an entire cache). For example, this allows embedded applications to lock
interrupt routines or other important (time-sensitive) instruction sequences into the instruction cache. It
allows data to be locked into the data cache, which may be important to code that must have deterministic
execution.
The processor core has a selectable 32- or 64-bit data bus and a 32-bit address bus. The processor core
supports single-beat and burst data transfers for memory accesses, and supports memory-mapped I/O
operations.
Figure 1-5 provides a block diagram of the MPC8240 processor core that shows how the execution units
(IU, FPU, BPU, LSU, and SRU) operate independently and in parallel. Note that this is a conceptual
diagram and does not attempt to show how these features are physically implemented on the chip.
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MPC8240 Integrated Processor Technical Summary
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Processor Core Overview
Figure 1-5. MPC8240 Integrated Processor Core Block Diagram
BRANCH
PROCESSING
UNIT
INSTRUCTION UNIT
INTEGER
UNIT
FLOATING-
POINT UNIT
FPR File
FP Rename
Registers
16Kbyte
D Cache
Tags
SEQUENTIAL
FETCHER
CTR
CR
LR
+
*
/
FPSCR
SYSTEM
REGISTER
UNIT
+
*
/
PERIPHERAL LOGIC
BUS INTERFACE
D MMU
SRs
DTLB
DBAT
Array
Touch Load Buffer
Copyback Buffer
64 Bit
32 Bit
Dispatch Unit
64 Bit
64 Bit
Power
Dissipation
Control
COMPLETION
UNIT
Time Base
Counter/
Decrementer
Clock
Multiplier
JTAG/COP
Interface
XER
I MMU
SRs
ITLB
IBAT
Array
16Kbyte
I Cache
Tags
64 Bit
64 Bit
64 Bit
64 Bit64 Bit
GPR File LOAD/STORE
UNIT
+
64 Bit
GP Rename
Registers
INSTRUCTION
QUEUE
+
32-/64-Bit Data Bus
32-Bit Address Bus
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MPC8240 Integrated Processor Technical Summary
Peripheral Logic Bus
1.3 Peripheral Logic Bus
The MPC8240 contains an internal peripheral logic bus that interfaces the processor core to the peripheral
logic. The core can operate at a variety of frequencies allowing the designer to balance performance and
power consumption. The processor core is clocked from a separate PLL, which is referenced to the
peripheral logic PLL. This allows the microprocessor and the peripheral logic to operate at different
frequencies while maintaining a synchronous bus interface.
The processor core-to-peripheral logic interface includes a 32-bit address bus, a 32- or 64-bit data bus as
well as control and information signals. The peripheral logic bus allows for internal address-only
transactions as well as address and data transactions. The processor core control and information signals
include the address arbitration, address start, address transfer, transfer attribute, address termination, data
arbitration, data transfer, data termination, and processor state signals. Test and control signals provide
diagnostics for selected internal circuits.
The peripheral logic interface supports bus pipelining, which allows the address tenure of one transaction
to overlap the data tenure of another. PCI accesses to the memory space are monitored by the peripheral
logic bus to allow the processor to snoop these accesses (when snooping not explicitly disabled).
As part of the peripheral logic bus interface, the processor coreÕs data bus is conÞgured at power-up to either
a 32- or 64-bit width. When the processor is conÞgured with a 32-bit data bus, memory accesses on the
peripheral logic bus interface allow transfer sizes of 8, 16, 24, or 32 bits in one bus clock cycle. Data
transfers occur in either single-beat transactions, or two-beat or eight-beat burst transactions, with a single-
beat transaction transferring as many as 32 bits. Single- or double-beat transactions are caused by noncached
accesses that access memory directly (that is, reads and writes when caching is disabled, caching-inhibited
accesses, and stores in write-through mode). Eight-beat burst transactions, which always transfer an entire
cache line (32 bytes), are initiated when a line is read from or written to memory.
When the peripheral logic bus interface is conÞgured with a 64-bit data bus, memory accesses allow transfer
sizes of 8, 16, 24, 32, or 64 bits in one bus clock cycle. Data transfers occur in either single-beat transactions
or four-beat burst transactions. Single-beat transactions are caused by noncached accesses that access
memory directly (that is, reads and writes when caching is disabled, caching-inhibited accesses, and stores
in write-through mode). Four-beat burst transactions, which always transfer an entire cache line (32 bytes),
are initiated when a block is read from or written to memory.
1.4 Peripheral Logic Overview
The peripheral logic block integrates a PCI bridge, memory controller, DMA controller, EPIC interrupt
controller/timers, a message unit with an Intelligent Input/Output (I
2
O) message controller, and an Inter-
Integrated Circuit (I
2
C) controller. The integration reduces the overall packaging requirements and the
number of discrete devices required for an embedded system.
Figure 1-6 shows the major functional units within the peripheral logic block. Note that this is a conceptual
block diagram intended to show the basic features rather than an attempt to show how these features are
physically implemented.
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Peripheral Logic Overview
Figure 1-6. MPC8240 Peripheral Logic Block Diagram
1.4.1 Peripheral Logic Features
Major features of the peripheral logic are as follows:
¥ Peripheral logic bus
Ñ Supports various operating frequencies and bus divider ratios
Ñ 32-bit address bus, 64-bit data bus
Ñ Supports full memory coherency
Ñ Decoupled address and data buses for pipelining of peripheral logic bus accesses
Ñ Store gathering on peripheral logic bus-to-PCI writes
¥ Memory interface
Ñ 1 Gbyte of RAM space, 16 Mbytes of ROM space
Ñ High-bandwidth, 64-bit data bus (72 bits including parity or ECC)
Ñ Supports fast page mode DRAMs, extended data out (EDO) DRAMs, or synchronous DRAMs
(SDRAMs)
Ñ Supports 1 to 8 banks of DRAM/EDO/SDRAM with sizes ranging from 1 to 128 Mbytes per
bank
Ñ Supports page mode SDRAMsÑfour open pages simultaneously
Ñ DRAM/EDO conÞgurations support parity or error checking and correction (ECC); SDRAM
conÞgurations support ECC
Ñ ROM space may be split between the PCI bus and the memory bus (8 Mbytes each)
Peripheral Logic
Address
Translator
DLL
Fanout
Buffers
PCI
Arbiter
Message
Unit
(with I2O)
I2C
Controller
DMA
Controller
Interrupt
Controller
EPIC
/Timers
PCI Bus
Interface Unit
Memory
Controller
Data Path
ECC Controller
Central
Control
Unit
32-Bit
System
Five
Request/Grant
Pairs
I2C
5 IRQs/
Peripheral Logic Block
Peripheral Logic
PLL
SDRAM
PCI
PCI Bus
Data (64-Bit)
Address Data Bus
(32- or 64-bit)
Memory/ROM/
Port X Control/Address
PCI Interface
Clock
Clock In
Clocks
Clocks
16 Serial
Interrupts
Bus
Configuration
Registers
(32-Bit) with 8-bit Parity
or ECC
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MPC8240 Integrated Processor Technical Summary
Peripheral Logic Overview
Ñ Supports 8-bit asynchronous ROM, or 32- or 64-bit burst-mode ROM
Ñ Supports writing to ßash ROM
Ñ ConÞgurable data path
Ñ Programmable interface timing
¥ PCI interface
Ñ Compatible with PCI Local Bus SpeciÞcation, Revision 2.1
Ñ Supports PCI locked accesses to memory using the LOCK signal and protocol
Ñ Supports accesses to all PCI address spaces
Ñ Selectable big- or little-endian operation
Ñ Store gathering on PCI writes to memory
Ñ Selectable memory prefetching of PCI read accesses
Ñ Interface operates at up to 66 MHz
Ñ Parity support
¥ Supports concurrent transactions on peripheral logic bus and PCI buses
1.4.2 Peripheral Logic Functional Units
The peripheral logic consists of the following major functional units:
¥ Peripheral logic bus interface
¥ Memory interface
¥ PCI interface
Ñ PCI bus arbitration unit
Ñ Address maps and translation
Ñ Big-and little-endian modes
Ñ PCI agent capability
Ñ PCI bus clock buffers and bus ratios
¥ DMA controller
¥ Message unit
Ñ Doorbell registers
Ñ Message registers
ÑI
2
O support (circular queues)
¥ Embedded programmable interrupt controller (EPIC) with four timers
¥I
2
C interface
1.4.3 Memory System Interface
The MPC8240 memory interface controls processor and PCI interactions to main memory. It supports a
variety of DRAM, and ßash or ROM conÞgurations as main memory. The MPC8240 supports FPM (fast
page mode), EDO (extended data out) and synchronous DRAM (SDRAM). The maximum supported
memory size is 1 Gbyte of DRAM or SDRAM and 16 Mbytes of ROM/ßash. SDRAM must comply with
the JEDEC SDRAM speciÞcation.
The MPC8240 implements Port X, a ßexible memory bus interface that facilitates the connection of general
purpose I/O devices. The Port X functionality allows the designer to connect external registers,
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MPC8240 Integrated Processor Technical Summary
13
Peripheral Logic Overview
communication devices, and other such devices directly to the MPC8240. Some devices may require a small
amount of external logic to properly generate address strobes, chip selects, and other signals.
The MPC8240 is designed to control a 32-bit or 64-bit data path to main memory DRAM or SDRAM. For
a 32-bit data path, the MPC8240 can be conÞgured to check and generate byte parity using four parity bits.
For a 64-bit data path, the MPC8240 can be conÞgured to support parity or ECC checking and generation
with eight parity/syndrome bits checked and generated.
The MPC8240 supports DRAM or SDRAM bank sizes from 1 to 128 Mbytes and provides bank start
address and end address conÞguration registers, but MPC8240 does not support mixed DRAM/SDRAM
conÞgurations. MPC8240 can be conÞgured so that appropriate row and column address multiplexing
occurs according to the accessed memory bank. Addresses are provided to DRAM and SDRAM through a
13-bit interface for DRAM and 14-bit interface for SDRAM.
Two bank selects, one write enable, one output enable, and up to 21 address signals are provided for ROM/
ßash systems.
1.4.4 Peripheral Component Interface (PCI)
The PCI interface for the MPC8240 is compatible with the Peripheral Component Interconnect
SpeciÞcation Revision 2.1. Mode-selectable, big- to little-endian conversion is supplied at the PCI interface.
The MPC8240 provides an interface to the PCI bus running at speeds up to 66 MHz.
The MPC8240Õs PCI interface can be conÞgured as host or agent. In host mode the interface acts as the main
memory controller for the system and responds to all host memory transactions.
In agent mode, the MPC8240 can be conÞgured to respond to a programmed window of PCI memory space.
A variety of initialization modes are provided to boot the device.
1.4.4.1 PCI Bus Arbitration Unit
The MPC8240 contains a PCI bus arbitration unit, which reduces the need for an equivalent external unit,
thus lowering system complexity and cost. It has the following features:
¥ The unit can be disabled to allow a remote arbitration unit to be used.
¥ Five external arbitration signal pairs. The MPC8240 is the sixth member of the arbitration pool.
¥ The bus arbitration unit allows fairness as well as a priority mechanism.
¥ A two-level round-robin scheme is used in which each device can be programmed within a pool of
a high- or low-priority arbitration. One member of the low-priority pool is promoted to the high-
priority pool. As soon as it is granted the bus, it returns to the low-priority pool.
1.4.4.2 Address Maps and Translation
The MPC8240Õs processor bus supports memory-mapped accesses. The address space is divided between
memory and PCI according to one of two allowable address maps. An in-bound and out-bound PCI address
translation mechanism is provided to support the use of the MPC8240 in agent mode. Note that only map
B is supported in agent mode.
When the MPC8240 is used as a peripheral processor and not the primary host, it is possible that only a
portion of the memory controlled by it may be visible to the system. In addition, it may be necessary to map
the local memory to different system memory address space. The address translation unit handles the
mapping of both in-bound and out-bound transactions for these cases.
1.4.4.3 Byte Ordering
The MPC8240 allows the processor to run in either big- or little-endian mode (except for the initial boot
code which must run in big-endian mode).
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MPC8240 Integrated Processor Technical Summary
Peripheral Logic Overview
1.4.4.4 PCI Agent Capability
In certain applications the embedded system architecture dictates that the MPC8240 act as peripheral
processor. In this case the peripheral logic must not act like a host bridge for the PCI bus. Instead it functions
as a conÞgurable device that is accessed by a host bridge. This capability allows multiple MPC8240 devices
to coexist with other PCI peripheral devices on a single PCI bus. The MPC8240 contains PCI 2.1-
compatible conÞguration capabilities.
1.4.5 DMA Controller
The integrated DMA controller contains two independent units, each capable of performing the following
types of transfers:
¥ PCI-to-local memory
¥ Local-to-PCI memory
¥ PCI-to-PCI memory
¥ Local-to-local memory
The DMA controller allows chaining through local memory-mapped chain descriptors. Transfers can be
scatter gathered and misaligned. Interrupts are provided on completed segment, chain, and error conditions.
1.4.6 Message Unit (MU)
Many embedded applications require handshake algorithms to pass control, status, and data information
from one owner to another. This is made easier with doorbell and message registers. The MPC8240 has a
message unit (MU) that implements doorbell and message registers as well as an I
2
O interface. The MU has
many conditions that can cause interrupts and uses the EPIC unit to signal external interrupts to the PCI
interface and internal interrupts to the processor core.
1.4.6.1 Doorbell Registers
The MPC8240 MU contains one 32-bit inbound doorbell register and one 32-bit outbound doorbell register.
The inbound doorbell register allows a remote processor to set a bit in the register from the PCI bus. This,
in turn, generates an interrupt to the processor core.
The processor core can write to the outbound register, causing the outbound interrupt signal INTA to assert,
thus interrupting the host processor. Once INTA is generated, it can be cleared only by the host processor
by writing ones to the bits that are set in the outbound doorbell register.
1.4.6.2 Inbound and Outbound Message Registers
The MPC8240 contains two 32-bit inbound message registers and two 32-bit outbound message registers.
The inbound registers allow a remote host or PCI master to write a 32-bit value, causing an interrupt to the
processor core. The outbound registers allow the processor core to write an outbound message which causes
the outbound interrupt signal INTA to assert.
1.4.6.3 Intelligent Input/Output Controller (I
2
O)
The intelligent I/O speciÞcation is an open standard that deÞnes an abstraction layer interface between the
OS and subsystem drivers. Messages are passed between the message abstraction layer from one device to
another.
The I
2
O speciÞcation describes a system as being made up of host processors and input/output platforms
(IOPs). The host processor is a single processor or a collection of processors working together to execute a
homogenous operating system. An IOP consists of a processor, memory, and I/O interfaces. The IOP
functions separately from other processors within the system to handle system I/O functions.
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MPC8240 Integrated Processor Technical Summary
15
Peripheral Logic Overview
The I
2
O controller of the MU enhances communication between hosts and IOPs within a system. The MU
maintains a set of FIFO buffers located in local IOP memory. Four queues are provided: two for inbound
messages and two for outbound messages. The inbound message queues are used to transfer messages from
a remote host or IOP to the processor core. The outbound queues are used to transfer messages from the
processor core to the remote host. Messages are transferred between the host and the IOP using PCI
memory-mapped registers. The MPC8240Õs I
2
O controller facilitates moving the messages to and from the
inbound and outbound registers and local IOP memory. Interrupts signal the host and IOP to indicate the
arrival of new messages.
1.4.7 Inter-Integrated Circuit (I
2
C) Controller
The I
2
C serial interface has become an industry de-facto standard for communicating with low-speed
peripherals. Typically, it is used for system management functions and EEPROM support. The MPC8240
contains an I
2
C controller with full master and slave functionality.
1.4.8 Embedded Programmable Interrupt Controller (EPIC)
The integrated hardware interrupt controller reduces the overall component count in embedded applications.
The embedded programmable interrupt controller (EPIC) is designed to collect external and internal
hardware interrupts, prioritize them, and deliver them to the processor core.
The module operates in two modes:
¥ In direct mode, Þve level- or edge-triggered interrupts can be connected directly to an MPC8240.
¥ The MPC8240 provides a serial delivery mechanism for when more than Þve external interrupt
sources are needed. The serial mechanism allows for up to 16 interrupts to be serially scanned into
the MPC8240. This mechanism increases the number of interrupts without increasing the number
of pins.
The outbound interrupt request signal, L_INT, is used to signal interrupts to the host processor when the
MPC8240 is conÞgured for agent mode. The MPC8240 EPIC includes four programmable timers that can
be used for system timing or for generating periodic interrupts.
1.4.9 Integrated PCI Bus and SDRAM Clock Generation
There are two clocking solutions directed towards different system requirements. For systems where the
MPC8240 is the host controller with a minimum number of clock loads, clock fan-out buffers are provided
on chip.
For systems requiring more clock fan out or where the MPC8240 is an agent device, external clock buffers
may be used.
1.4.10 Bus Ratios
The MPC8240 requires a single clock input signal, PCI_SYNC_IN, which can be driven by the PCI clock
fan-out buffersÑspeciÞcally the PCI_SYNC_OUT output. PCI_SYNC_IN can also be driven by an
external clock driver.
PCI_SYNC_IN is driven by the PCI bus frequency. An internal PLL, using PCI_SYNC_IN as a reference,
generates an internal peripheral bus clock that is used for the internal logic. The peripheral bus clock
frequency is selectable by the MPC8240 PLL conÞguration signals (PLL_CFG[0Ð4]) to be a multiple of the
PCI_SYNC_IN frequency.
The MPC8240 provides an on-chip delay-locked loop (DLL) that can supply an external memory bus clock
to SDRAM banks. The memory bus clock is of the same frequency and synchronous with the internal
peripheral bus clock.
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16
MPC8240 Integrated Processor Technical Summary
Power Management
The internal clocking of the processor core is generated from and synchronized to the internal peripheral
bus clock by means of a second PLL. The coreÕs PLL provides multiples of the internal processor core clock
rates as speciÞed in the
MPC8240 Hardware SpeciÞcation.
1.5 Power Management
The MPC8240 provides both automatic and program-controllable power reduction modes for progressive
reduction of power consumption.
The MPC8240 has independent power management functionality for both the processor core and the
peripheral logic. The MPC8240 provides hardware support for three levels of programmable power
reduction for both the processor and the peripheral logic. Doze, nap, and sleep modes are invoked by register
programmingÑHID0 in the case of the processor core and conÞguration registers in the case of the
peripheral logic block. The processor and peripheral logic blocks are both fully static, allowing internal
logic states to be preserved during all power-saving modes. The following sections describe the
programmable power modes.
1.5.1 Programmable Processor Power Management Modes
Table 1-1 summarizes the programmable power-saving modes for the processor core. These are very similar
to those available in the MPC603e device.
1.5.2 Peripheral Logic Power Management Modes
The following subsections describe the power management modes of the peripheral logic. Table 1-2
summarizes the programmable power-saving modes for the peripheral logic block.
Table 1-1. Programmable Processor Power Modes
PM Mode Functioning Units Activation Method Full-Power Wake Up Method
Full power All units active Ñ Ñ
Full power
(with DPM)
Requested logic by
demand
By instruction dispatch Ñ
Doze Bus snooping
Data cache as needed
Decrementer timer
Controlled by software
(write to HID0)
External asynchronous exceptions
(assertion of SMI or
int
),
Decrementer exception
Hard or soft reset
Machine check exception (
mcp
)
Nap Decrementer timer Controlled by software
(write to HID0) and
qualiÞed with QACK from
peripheral logic
External asynchronous exceptions
(assertion of SMI, or
int
)
Decrementer exception
Negation of QACK by peripheral logic
Hard or soft reset
Machine check exception (
mcp
)
Sleep None Controlled by software
(write to HID0) and
qualiÞed with QACK from
peripheral logic
External asynchronous exceptions
(assertion of SMI, or
int
)
Negation of QACK by peripheral logic
Hard or soft reset
Machine check exception (
mcp
)
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MPC8240 Integrated Processor Technical Summary 17
Debug Features
.
1.6 Debug Features
The MPC8240 includes the following debug features:
¥ Memory attribute and PCI attribute signals
¥ Debug address signals
¥ MIV signal: Marks valid address and data bus cycles on the memory bus.
¥ Error injection/capture on data path
¥ IEEE 1149.1 (JTAG)/test interface
1.6.1 Memory Attribute and PCI Attribute Signals
The MPC8240 provides additional information corresponding to memory and PCI activity on several
signals to assist with system debugging. The two types of attribute signals are described as follows:
¥ The memory attribute signals are associated with the memory interface and provide information
concerning the source of the memory operation being performed by the MPC8240.
¥ The PCI attribute signals are associated with the PCI interface and provide information concerning
the source of the PCI operation being performed by the MPC8240.
Table 1-2. Programmable Peripheral Logic Power Modes
PM
Mode Functioning Units Activation Method Full-Power Wake Up
Method
Full
power
All units active Ñ Ñ
Doze PCI address decoding and bus arbiter
System RAM refreshing
Processor bus request and NMI monitoring
EPIC unit
I2C unit
PLL
Controlled by software
(write to PMCR)
PCI access to memory
Processor bus request
Assertion of NMI
Interrupt to EPIC
Hard Reset
Nap PCI address decoding and bus arbiter
System RAM refreshing
Processor bus request and NMI monitoring
EPIC unit
I2C unit
PLL
Controlled by software
(write to PMCR) and
processor core in nap or
sleep mode
PCI access to memory1
Processor bus request
Assertion of NMI
Interrupt to EPIC
Hard Reset
1 A PCI access to memory in nap mode does not cause QACK to negate; subsequently, it does not wake up the
processor core. Thus the processor wonÕt snoop this access. After servicing the PCI access, the peripheral
logic automatically returns to the nap mode.
Sleep PCI bus arbiter
System RAM refreshing (can be disabled)
Processor bus request and NMI monitoring
EPIC unit
I2C unit
PLL (can be disabled)
Controlled by software
(write to PMCR) and
processor core in nap or
sleep mode
Processor bus request
Assertion of NMI
Interrupt to EPIC
Hard Reset
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18 MPC8240 Integrated Processor Technical Summary
Debug Features
1.6.2 Memory Debug Address
When enabled, the debug address provides software disassemblers a simple way to reconstruct the 30-bit
physical address for a memory bus transaction to DRAM and SDRAM, ROM, FLASH, or PortX. For
DRAM or SDRAM, these 16 debug address signals are sampled with the column address and chip-selects.
For ROMs, FLASH, and PortX devices, the debug address pins are sampled at the same time as the ROM
address and can be used to recreate the 24-bit physical address in conjunction with ROM address. The
granularity of the reconstructed physical address is limited by the bus width of the interface; double-words
for 64-bit interfaces, words for 32-bit interfaces, and bytes for 8-bit interfaces.
1.6.3 Memory Interface Valid (MIV)
The memory interface valid signal, MIV, is asserted whenever FPM, EDO, SDRAM, FLASH, or ROM
addresses or data are present on the external memory bus. It is intended to help reduce the number of bus
cycles that logic analyzers must store in memory during a debug trace.
1.6.4 Error Injection/Capture on Data Path
The MPC8240 provides hardware to exercise and debug the ECC and parity logic by allowing the user to
inject multi-bit stuck-at faults onto the peripheral logic or memory data/parity busses and to capture the data/
parity output on receipt of an ECC or parity error.
1.6.5 IEEE 1149.1 (JTAG)/Test Interface
The processor core provides IEEE 1149.1 functions for facilitating board testing and debugging. The IEEE
1149.1 test interface provides a means for boundary-scan testing the processor core and the board to which
it is attached.
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MPC8240 Integrated Processor Technical Summary 19
Debug Features
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Mfax is a trademark of Motorola, Inc.
The PowerPC name, the PowerPC logotype, and PowerPC 603e are trademarks of International Business Machines Corporation used by Motorola
under license from International Business Machines Corporation.
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