6.42
IDT71V30S/L
High-Speed 1K x 8 Dual-Port Static RAM with Interrupts Industrial and Commercial Temperature Ranges
13
Functional Description
The IDT71V30 provides two ports with separate control, address
and I/O pins that permit independent access for reads or writes to any
location in memory. The IDT71V30 has an automatic power down
feature controlled by CE. The CE controls on-chip power down circuitry
that permits the respective port to go into a standby mode when not
selected (CE = VIH). When a port is enabled, access to the entire
memory array is permitted.
Interrupts
If the user chooses the interrupt function, a memory location (mail
box or message center) is assigned to each port. The left port interrupt
flag (INTL) is asserted when the right port writes to memory location
3FE (HEX), where a write is defined as the CE = R/W = VIL per Truth
Table II. The left port clears the interrupt by accessing address location
3FE access with CER = OER = VIL, R/W is a "don't care". Likewise, the
right port interrupt flag (INTR) is asserted when the left port writes to
memory location 3FF (HEX) and to clear the interrupt flag (INTR), the
right port must access the memory location 3FF. The message (8 bits)
at 3FE or 3FF is user-defined, since it is an addressable SRAM location.
If the interrupt function is not used, address locations 3FE and 3FF are not
used as mail boxes, and are part of the random access memory. Refer
to Table II for the interrupt operation.
Busy Logic
Busy Logic provides a hardware indication that both ports of the
SRAM have accessed the same location at the same time. It also
allows one of the two accesses to proceed and signals the other side
that the SRAM is “Busy”. The BUSY pin can then be used to stall the
access until the operation on the other side is completed. If a write
operation has been attempted from the side that receives a BUSY
indication, the write signal is gated internally to prevent the write from
proceeding.
The use of BUSY logic is not required or desirable for all applica-
tions. In some cases it may be useful to logically OR the BUSY outputs
together and use any BUSY indication as an interrupt source to flag the
event of an illegal or illogical operation.