IBM System/360 Operating Guide

Selector-Channel Tags
The nine tag indicators for each selector channel
perform the same functions as the corresponding
indicators for the multiplexor channel (see MPX
Channel Tags section).
Selector-Channel Checks
Each selector channel has a number of check
circuits that continually monitoF channel operation.
When a malfunction is detected, the appropriate
check light is turned on. These checks are:
IL. If the SLI flag is...!!Qi on, this light (incorrect
length condition) is turned on when the number of
bytes in the assigned storage area is not equal to
the number of bytes requested or offered by the
I/O unit.
PROG. This light (program check) indicates that
the channel has detected a programming error.
PROT. This light (protection check) indicates
that the channel attempted to violate a portion
of main storage that is protected for the cur-
rent operation.
CHNL Data.. This light (channel data check)
indicates that the channel has detected a parity
error in the information transferred to or from
main storage during an I/O operation.
CHNL CTRL. This light (channel control check)
indicates that a machine malfunction affecting
channel controls has occurred.
INT Face. The interface control check is caused
by sequencing problems on the I/O interface.
Read-Only Storage Displays
In general, these indicators are for Customer
Engineering use. Therefore, only a short descrip-
tion of each ROS field is presented here.
CA, CB, CC, CF, CG, CV. These fields control
operation of the ALU.
CD. This field selects one of the several system
registers to receive the output of the ALU. A
given register can be used as both the source and
destination during a single ROS cycle.
18
CK. This field provides a source of data and con-
trol bits (that is, generates constants).
CM, CU. These two fields control storage opera-
tion. They determine which storage area (main
or auxiliary) is to participate in a particular read
or write operation.
CN, CH, C L. These fields control the address of
the next ROS word.
LP. This light indicates that the air pressure in
the read-only storage unit is low, or that the
temperature of main storage is below the optimum
operating range.
w- and X-Register. These indicators display the
address of the ROS word just read.
CS. This field supplies status indications to various
machine control points.
USE METERS
The 2030 console has two direct-reading meters
that measure operating time; a customer's meter
and a Customer Engineer's meter. The position of
a key switch determines whether the customer's
meter or the CE meter is operating. The Customer
Engineer holds the key for this switch; and whenever
he is performing either scheduled or unscheduled
maintenance in the CPU, he will set the switch to
cause the CE meter to operate. One of these meters
(determined by key-switch setting) operates when-
ever the CPU clock is running and either:
1. The CPU is not in the wait state or,
2. There is an interruption pending, or
3. A manual store or dis play operation is in
progress. The System indicator is on when
either meter is running. It indicates that some
productive activity is in progress. The System
light stays on as long as any I/o unit (except
the 1050) is engaged in an I/O operation (that
is until device-end occurs for the last command
in a chain for that I/O device). This can occur
after the Stop key is pressed.
The use meter (customer or CE) operates
for a minimum of 400 milliseconds each time
it is started.

IBM System/360 Specifications

General

Brand	IBM
Model	System/360
Category	Desktop
Language	English