User Manual PLC-3 FAMILY I/0 Instruction Manual

Binary Command Language
Appendix A
A-24
When the processor receives a read-modify-write command,
it (Figure A.3):
1. Reads the data at the specified address.
2. Performs a logical AND operation between the data read in step 1 and
the AND mask.
3. Performs a logical OR operation between the result of step 2 and the
OR mask.
4. Writes the result of step 3 into the word at the specified address.
Figure A.3
ReadModifyWrite
Operation
Bit Pattern Description
1111000011110000 Initial state of specified word
0101010101010101 AND mask
0101000001010000 Result of logicalAND operation
1010000001011111 Final result
The processor responds to a read-modify-write command with one of the
following response codes:
Response Codes
Hex Description
00 Success
04 Address unknown
06 Access not allowed
08 Address not complete
0F No privilege
The following response block shows a successful read-modify-write
command:
STX
02
OSC
01
SIZ
01
RSP
00
ETX
03
CHK
07