Ccu Diagnostics; Ccu Error Handling - IBM 3745 Maintenance Information Reference

CCU Diagnostics
The CCU has diagnostic facilities designed to allow the program to perform test
procedures on the controller hardware. The test routines. can be either part of
the online control program or a stand-alone control program used for testing
purposes only. If these test routines are part of the online control program, the
telecommunication lines and adapters not being tested are allowed to continue
operating.
The following operations are available for program use:
1. Set and reset the bypass CCU check stop mode. Output X79', byte 1, bit 4
set to 1 prevents CCU hard stop and MOSS interrupt from being set due to
a CCU hard check. To reset the bypass mode, the control program must
execute an -output X'79' instruction with byte 1, bit 5 set to 1.
However, MOSS can also issue a bypass CCU check stop or a CCU hard
stop. The following table shows the resulting CCU mode.
MOSS PGM
CCU Mode Result
- -
Normal
*
-
Bypass Bypass
Bypass
-
Bypass
Bypass Bypass Bypass
Bus stop (1)
-
Normal
*
Bus stop (1) Bypass Normal
*
Bus stop Bypass
and Bypass
*
See "CCU Error Handling" and "Program Errors" on page 2-51.
(1): Adapter interface check stop causes adapter interface errors to be
handled as hard errors.
2. Set and reset the L 1 adapter mask. Program level 1 interrupt requests
caused by a check condition in an adapter (scanner or CA) can be masked
by using an output X'7E', byte 1, bit 1. To unmask the level 1 requests, the
control program must execute an output X'7F' (reset mask bits) with byte 1,
bit 1 set to 1.
3. Force CCU checks. The control program can use the output X'78' instruc-
tion which will result in an ALU compare error and wrong parity on ALU
result.
CCU Error Handling
The following are the basic principles of the CCU error handling strategy:
• CCU-detected hard errors:
They are high severity errors, usually hardware failures. They stop the
CCU. No retry is performed. The error indication latches are sensed by
MOSS through the LSSD path.
• CCU-detected non-hard errors:
Chapter 2. Central Control Unit (CCU)
2-47