IBM 2790, Manual

Page: 59 / 88

is executed and a meaningful System/360 error printout
is made available. The formatting consists of a translation
from binary to EBCDIC English language.
2715 Diagnostics
The 2715 diagnostic programming consists of one System/360
coded program and numerous 2715 microcoded test routines.
The System/360 program is a 2715 System Exerciser
Program. It functionally tests a 2715 system in a multi­
plexing environment similar to that encounted in a customer
operation. It reports all detectable system errors and failures
and logs statistics on system usage at all levels. It may be
used for 2715 system installation, verification, or testing.
The 2715 microcoded diagnostic test routines perform
the primary 2715 system maintenance facility. They reside
on the 2715 disk and are executed within the 2715 auto­
matically or upon CE request. There are two general classes
of test routines:
1. 2715 Hardware
2. 2715 Device
Hardware Tests
The 2715 hardware test routines isolate hardware failures
in each of the following areas of the 2715:
Data Flow and Storage
Channel Adapter
BSC Adapter
Disk Adapter
2790 Adapter
2740 Adapter
Device Tests
The 2715 device test routines isolate functional and hard­
ware failures in the devices attached to the 2715. The degree
of failure isolation provided by these tests is a function of
the isolation facility provided by the device. The following
devices are supported:
Integral Disk
2740 Communication Terminal
2790 Loop
Area Station, with:
Key Entry
Card Readers
1053 Printers
Data Entry Units
Badge Readers
Multiplexer Channel Error Recovery Procedures
An I/O error causes an interrupt condition. The condition
causing the interrupt is indicated in the Channel Status
Word (CSW) if the Unit Check bit (bit 38) is present in the
CSW. A Sense command must be performed to obtain
further information about the error interrupt.
Hardware-Detected Errors
System/360 Interface I/O Bus-Out Check. All information
transferred on ‘I/O bus out’ requires proper parity. An
improper
address byte (bad parity) during Start I/O is
detected as an invalid address, thus preventing selection and
attachment of the 2715.
The processor is notified of command parity errors by
‘sense bus out check’. In this situation the processor should
initiate a retry procedure.
The use of binary synchronous data-link control enables
the adapter to retry if data errors are detected during out­
put transactions.
System/360 Interface I/O Bus-In Check. All data input to
the channel is checked for correct parity. Parity is generated
from the eight information bits to ensure correct communi­
cation on the interface. This generated parity is compared
with the associated parity position of the data register
transferred to the bus.
During data transfer the message is aborted by use of
‘bi-sync block cancel’, upon which a retry is initiated.
Microcode-Detected Errors
Checking is implemented at critical points within the adapter
microcode. The purpose of this checking is to prevent loss
of control due to hardware/program interface malfunction.
Error recovery in such a situation may simply return control
to the 2715 supervisor. All errors within the adapter are
recorded.
Multiplexer Channel Adapter Microdiagnostics
All adapter hardware—with the exception of System/360
interface drivers and terminators and the gating circuits to
and from these—may be tested by 2715 diagnostic routines
resident on disk. The microdiagnostics are intended as a
method of fault location and are used successfully only
when the adapter is isolated from the System/360 interface.
Therefore, the inactive state is a prerequisite for diagnostic
capability in the channel adapter—that is, the 2715 must be
off-line with respect to System/360.
Error Procedures
59