HD64570 Datasheet, PDF (348/469 Pages) Hitachi Semiconductor – Serial Communications Adaptor

Reception Processing Routine: Two examples of reception processing routines are given in
figures 9.3 and 9.4.
Start
Load TRB
contents to ACC
Transfer ACC
data to memory
CRC code
Yes
being received?
No
Load ACC contents
(data) to B register
Second CRC
Yes
code byte being
received?
No
Next data is second
CRC code byte
Issue RX CRC
calculation forcing
command
(CMD ← 00011000)
Wait for 15 system
clock cycles
Read ST2 contents
to memory
ACC data = ETX? ^Yes
No
Next data is
CRC code
Issue message
reject command
(CMD ← 00010101)
Issue EI instruction
Return
ACC: Accumulator
TRB: TX/RX buffer register
CMD: Command register
ST2: Status register 2
EOM: End of message command
ETX: Control character (end of text)
ETB: Control character (end of block)
Figure 9.3 RXRDY Interrupt Processing Routine (using HD64180)
Rev. 0, 07/98, page 332 of 453