RD-LAP/MDC4800 Motient/ARDIS CMX969
2001 Consumer Microcircuits Limited 18 D/969/5
'Frame Sync' Values written to Data Block Buffer
Symbols Binary Hex
-1 +1 -1 +1 Byte 0: 00100010 22
-1 +3 -3 +3 Byte 1: 00110111 37
-3 -1 +1 -3 Byte 2: 01001001 49
+3 +3 -1 +1 Byte 3: 11110010 F2
-3 -3 +1 +3 Byte 4: 01011011 5B
-1 -3 +1 +3 Byte 5: 00011011 1B
NULL:
This ‘task’ has no effect in transmit mode.
T40B: Transmit 40 Bits (MDC only)
This task is similar to the RD-LAP mode T24S task, but transmits 40 bits taken from the first 5 bytes in the
Data Block Buffer. Data block buffer byte 0 is transmitted first, byte 4 last, within each byte the msb is
transmitted first, lsb last.
THB: Transmit Header Block (RD-LAP and MDC)
In RD-LAP mode this task takes 10 bytes of data from the Data Block Buffer, calculates and appends the 2-
byte CRC1 checksum, translates the result to 4-level symbols (with FEC), interleaves the symbols and
transmits the result as a formatted 'Header' Block , inserting 'S' symbols at 22-symbol intervals.
In MDC mode this task takes 4 bytes of data from the Data Block Buffer, calculates and appends the 2-byte
checksum, adds FEC bits, interleaves the result, inserts channel status bits and transmits the result as a
formatted 'Header' Block..
Once the modem has read the data bytes from the Data Block Buffer, the BFREE and IRQ bits of the Status
Register will be set to '1'.
TIB: Transmit Intermediate Block (RD-LAP and MDC)
In RD-LAP mode this task takes 12 bytes of data from the Data Block Buffer, updates the 4-byte CRC2
checksum for inclusion in the 'Last' block, translates the 12 data bytes to 4-level symbols (with FEC),
interleaves the symbols and transmits the result as a formatted 'Intermediate' Block , inserting 'S' symbols at
22-symbol intervals.
In MDC mode this task takes 6 bytes of data from the Data Block Buffer, updates the 2-byte CRC checksum
for inclusion in the 'Last' block, adds FEC bits, interleaves the result, inserts channel status bits and transmits
the result as a formatted ‘Intermediate’ Block.
Once the modem has read the data bytes from the Data Block Buffer, the BFREE and IRQ bits of the Status
Register will be set to '1'.
TLB: Transmit Last Block (RD-LAP and MDC)
In RD-LAP mode this task takes 8 bytes of data from the Data Block Buffer, updates and appends the 4-byte
CRC2 checksum, translates the resulting 12 bytes to 4-level symbols (with FEC), interleaves the symbols
and transmits the result as a formatted 'Last' Block , inserting 'S' symbols at 22-symbol intervals.
In MDC mode this task takes 4 bytes of data from the Data Block Buffer, updates and appends the 2-byte
checksum, adds FEC bits, interleaves the result, inserts channel status bits and transmits the result as a
formatted ‘Last’ Block.