Figure 15: Example Of Mailbox Communication - WAGO I/O-SYSTEM 750 Manual

WAGO-I/O-SYSTEM 750
®
750-644 Bluetooth RF-Transceiver
The figure "Example of Mailbox communication" describes the request and
processing of a Mailbox command. The process data are shown as follows:
[ Parameter 0-x | Toggle | Opcode | int. Byte | Control/Status Byte ]
First, any process data may be present in the output and input process image. The
PLC application then maps the Mailbox by setting bit 5 in the control byte and the
750-644 I/O module responds with bit 5 in the status byte. Initially, no specific
process is started, rather the entire request is written with value 0, i.e. IDLE. By
the 750-644 I/O module responding to IDLE, it indicates its readiness to process
other operations. Next, the PLC application starts a request in which a value is
requested by the 750-644 I/O module. The PLC application writes the modified
opcode and associated parameter data to the PIO. The 750-644 I/O module
responds with a mirrored opcode and requested value as parameter data of the
response. By the PLC application then inverting the toggle bit, it requests the
same value again from the 750-644 I/O module. The 750-644 I/O module again
responds with a mirrored opcode and toggle bit, as well as the current value in the
parameter data of the response. The PLC application then hides the Mailbox
again.

Figure 15: Example of Mailbox communication

Manual
Version 2.0.0, valid from FW/HW Version 03/03
Process Image 57