IBM System/360 2050 User Manual

Load From Disk
When loading FLT's from disk, the procedure is
slightly different. First the FLT mode switch is
set to the off position and the system reset PB is
depressed, thus setting the cylinder counter (KH553-
554) to zero. The FLT mode switch is then set in
the load position and the load PB is depressed. The
FLT load from disk resets the IAR to zero, sets the
sequence counter mode trigger on, and simulates a
start 1/0 operation with a control seek command.
The control seek command initiates a series of three
write fetch priority 2 requests (priority 2, control
1-3). The disk unit terminates the operation after
accepting six bytes of seek data. As a read data
command is command-chained to the control seek
command, the FLT controls wait for a fourth
priority 2 request (CCWl). When this CCWl arrives,
the read data command takes over control and the
system proceeds to read in data. If a unit check or
a channel data check is sensed at the end of the con-
trol seek operation, command chaining is suppressed
and the FLT controls hang up.
Unsuccessful Load
When loading FLT's from either tape or disk, and
a parity check, wiit check, or channel data check
occurs during the read data operation, the FLT load
check indicator turns on and loading continues to the
end of the record. (A unit check or channel data
check is shown on CPU roller 2, positions 6 and 12,
respectively.) Next the CPU stops or attempts to
reread the record, depending on the FLT control
switch setting. The retry and backspace triggers in
conjunction with the FLT control switch are used to
control the rereading of a bad record received from
tape.
A FLT load hangs up prior to completion if either
the selector char.nel or the FLT load controls fail
to operate correctly. Failures of this type are
diagnosable from the sequence stat and sequence
counter indicators using Figure 25 or 26.
Completion of Successful Load
At the completi0i1 of a successful FLT load, the
supervisory controls are set to main store mode,
and execution starts at location four. (Locations
zero through three are used for record identification. )
Main store mode hardcore tests and the ROS bit
tests are executed in this (main store) mode. When
the ROS mode hardcore or cycle tests are to be
executed, op code 06 (in the FLT op reg) will put
the CPU in ROS mode.
The following sequence of words at the beginning
of each FLT record in storage is used to initiate the
ROS mode cycle tests.
Word
~Operation
~
0-3
Identification
0-3 Machine type (Mod 50
=A)
4-7 Type of teat
5 = Zero-cycle test
6 = One-cycle test
8-11 Zeros
12-15 Segment number
16-27 EC Level
28-31
Undefined
2
4-7 SOR to ROAR FOB (hex) In bits 19-30
and reset bin- 0111 In parity bits (MS mode)
ary trigger
3
8-11
Call for ROS
0110 In parity bits (MS mode)
mode
·4 12-15 Turn on Ignore F3A (hex) In bits 19-30; ones
error trigger In bits 2, 5, and 6; zeros else-
where
5 16-19 Reset pass/ F44 (hex) in bits 19-30; zeros
fail triggers elsewhere
6 20-23 Reset binary Addre11s of first test in bits
trigger and 8-31
error register,
branch to first
test
The first word in this sequence is not used.
(Location zero is never accessed.) The second
word, which is executed from storage locations
4-7, forces the entry address of the fetch LCW
kernel into ROAR. Thus when the third word causes
ROS mode control, the fetch LCW kernel is executed.
Words 4-6 are then executed in sequence under ROS
control. Word 6 allows branching to any starting
address and contains the location of the first word
of scan-in data. Normal FLT execution is now in
effect.
MAIN STORE MODE FLT's
Main store mode FLT's consist of hardcore tests
and tests for checking out ROS. These tests are on
a tape separate from ROS mode FLT's and are
normally run first. They are the first step in a
"bootstrap" checkout procedure aimed at exercising
hardware and validating its operation before using
it to control the checkout of other hardware. These
tests are loaded via an FLT load operation. Main
store mode tests may be terminated by:
1. A system reset
2. A call for FLT load (op code OA)
3. A request for ROS mode (op code 06)
Maintenance Features (3/71) 45

IBM System/360 2050 Specifications

General

Brand	IBM
Model	System/360 2050
Category	Computer Hardware
Language	English