User manual

109
Function codes included in the query
Each function code is 1 byte. When the PLC receives a query (Q), the
function code of the final response (R) is formed by adding $80 (hex) to
the function code sent by the query. The value added to the function
code sent by the query differs for 2-step and 4-step by $20 (hex).
The function code of the R message can be used by the peripheral
device to verify that the correct Q message has been received by the
PLC.
Communication function codes
$ notes hexadecimal notations
The bit/word address assignment uses the absolute address method
for reading memory locations. (Refer to Absolute Addressing on
Chapter 3)
Please contact our technical support for more information about
reading/writing program or other function codes.
Query, which dictionary meaning is `question’, `ask’, or `question mark’,
means that a user or an application program requests any specific
information to a corresponding part when it is used as a
communication term.
Communication
function
Query (Q)
function code
Response (R)
function code
Remarks
2-step 4-step 2-step 4-step
Read bits $21 $01 $A1 $81 Detailed description
Write bits $22 $02 $A2 $82
“
Read words $23 $03 $A3 $83
“
Write words $24 $04 $A4 $84
“
Read bits and words $25 $05 $A5 $85
“
Write bits and words $26 $06 $A6 $86
“
Read program $27 $07 $A7 $87 No detailed description
Write program $28 $08 $A8 $88
“
Read instruction $29 $09 $A9 $89
“
Change instruction $2A $0A $AA $8A
“
Change operand $2B $0B $AB $8B
“
Insert instruction $2C $0C $AC $8C
“
Delete instruction $2D $0D $AD $8D
“
Search instruction $2E $0E $AE $8E
“
Search operand $2F $0F $AF $8F
“
Delete all/parts of program $20 $10 $A0 $90
“
No service $00 $00 $00 (hex) $00 (hex)
“