Diagnostic Aids; Communications Diagnostic Buffer; Displaying The Diagnostic Buffer - IBM 5100 Maintenance Information Manual

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Much of the hardware and many of the microprograms used
during communications and serial I/O are also used in APL
or BASIC language operations. You should run all the hard-
ware diagnostic programs for better isolation when trouble-
shooting a communications or serial I/O problem. These
diagnostic programs are described in the IBM 5100 Maint-
enance Information Manual.
Wrap connectors (P/N 1608894 and PIN 1608382) are re-
quired for the MD I (maintenance diagnostic integrated)
program MD I 820. The wrap connectors can be attached
to the end of the cables or to the 5100 communications or
serial I/O connector. The wrap connectors connect the
line request to send to clear to send, the line data terminal
ready to data set ready, and transmitted data to received
data. This allows the communications/serial I/O diagnostic
MOl 820 to check the control and data lines with the 5100
Portable Computer isolated from the data set or serial I/O
device. If the wrap connector is attached to the end of
the data set or serial I/O adapter cable, the cable can also
be tested. Refer to the IBM 5100 Maintenance Information
Manual for the internal wiring of the wrap connectors.
COMMUNICATIONS DIAGNOSTIC BUFFER
All characters transmitted or received during communica-
tions are placed in the communications diagnostic buffer.
This buffer is a 256-byte buffer in read/write storage; it is
used to store all transmit and receive data. All characters
(including control and function characters that are not
normally displayed on the screen) that are received from or
transmitted to the communications line are stored in the
buffer. Therefore, the buffer can be used to isolate prob-
lems between the 5100 and the communications network.
Because the diagnostic buffer can contain only 256 char-
acters, you might find it necessary to stop the communi-
cations operation to check the data desired.
You can stop the communications operation when you are
transmitting data from the 5100 keyboard as follows:
1. Enter the data from the keyboard and press the
EXECUTE key.
2. Press and hold the shift key.
Diagnostic Aids
3. Press the ATTN key.
4.
Display the diagnostic buffer. (See Displaying the
Diagnostic Buffer.)
You can stop the communications operation when the 5100
is transmitting data from tape as follows:
1. Press and hold the shift key.
2.
Press the ATTN key.
3. Release the shift key and press the ATTN key again.
The tape operation stops and you can display the data in
the buffer. (See Displaying the Diagnostic Buffer.)
You can stop the communications operation when the
5100 is receiving data as follows:
1. Press and hold the CMD key.
2. Press the ATTN key. (This procedure will cause
the rest of the message to be lost and you might
have to sign on or dial the remote system again to
resume the receive operation.)
The receive operation will stop and you can display the last
256 bytes of data received in the buffer. (See Displaying
the Diagnostic Buffer.)
Displaying the Diagnostic Buffer
To display the diagnostic buffer, enter the command
~DIAG
0 (zero) as follows:
1. Press and hold the CMD key and press the 1 key.
The character & is displayed on the screen.
2. Enter DIAG space 0 (zero) and press EXECUTE.
Refer to CE Display while reading the following description
of how the data is displayed.
Diagnostic Aids 3-1