Table 31: Structure Of The Process Image When The Mailbox Is Visible - WAGO I/O-SYSTEM 750 Manual

WAGO-I/O-SYSTEM 750
®
750-644 Bluetooth RF-Transceiver

Table 31: Structure of the process image when the Mailbox is visible

Byte(s)
0
1
2
3
4 ... 7,
4 ... 13 or
4 ... 19
Rest
The so-called opcode defines the operating to be processed by the I/O module.
The opcode determines how many bytes are occupied by parameter data in the
request and response or how many bytes are populated with the value 0 in the
back part of the area overlaid by the Mailbox (null bytes).
The toggle byte consists of two parts:
• Bit 7 serves as a toggle bit
-
-
• Bits 6 ... 0 contain the so-called return code.
The return code in the process image of the inputs provides more detailed
information about whether execution of the request was successful or
whether errors have occurred.
All processes within the Mailbox follow the request/response principle:
1. A request is made in the PIO. This can be generated by a PLC application,
for example.
2. The I/O module generates a response in the PII.
There is a request when the value of the opcode or toggle byte changes in the PIO
compared to the previous status. The 750-644 I/O module then evaluates the
entire request including any parameters and starts to process the requested
operation.
Manual
Version 2.0.0, valid from FW/HW Version 03/03
Assignment
Control/status byte
-
Mailbox:
Opcode
Mailbox:
Toggle byte
Mailbox:
Parameters and/or
null bytes
Process data
The toggle bit in the output process image (PIO) is used to make
repeated requests with the same opcode distinguishable.
The toggle bit in the input process image (PII) is used to confirm
execution of requests in general.
Description
See section "Process Image" > ... >
"Control/Status Byte"
-
See description below.
See section "Process Image" > ... >
"Process Data"
Process Image 55