Rockwell Automation 8520 9/Series CNC Integration Maintenance Manual Documentation Set - Manual (Page 519)

Chapter 9B
Integrating Your Teach Pendant
9B-8
If the teach pendant does not respond, a watchdog timeout occurs and:
$TPTO is set
an error message is displayed on the operator panel CRT
PAL can control the activities in response to the timeout
system continues to send watchdog signals to try and reestablish
communication. When the system receives a correct response packet,
the control sets $TPTO to false.
A watchdog timeout can also occur if 3 ENQs are sent to the teach pendant
in response to NAKs.
Receiving Error Messages
If requested by the teach pendant with a CMD 61 (hex) and SD1=04, when
the control displays an error message, it also sends the message in ASCII
to the teach pendant:
CMD SD1 SD2 SD3 TNS TNS DATA
DLE STX 62 02 00 00 00 04 PAL DOES NOT EXIST NULL DLE ETX BCC
ASCII
The teach pendant does not have to respond to the message. It only has to
send an ACK or a NAK.
If you send an illegal request from the teach pendant to the control, the
control sends a message back telling you about the illegal request. In the
message from the control the SD2 and SD3 fields contain the information
that identifies the illegal request:
This Field Contains this Information about the Illegal Request
SD2 CMD value received
SD3 SD1 value received
For example, if the teach pendant sends this illegal request:
CMD SD1 SD2 SD3 TNS TNS
DLE STX 71 02 00 00 00 41 DLE ETX BCC
The teach interface software responds with:
CMD SD1 SD2 SD3 TNS TNS
DLE STX 63 00 71 02 00 21 DLE ETX BCC
To the teach interface software, an illegal request is any request that does
not match those defined in this section.
END OF SECTION
9B.7
Receiving the Illegal
Request Message from the
CNC
(CMD=63 hex)