system (continued)
control instructions 103 damage (machine-check interruption condition) 178
indicator 247
operation, I/O 189
organization 13
program 10 recovery (machine-check interruption condition) 178, 175
reset, I/O 194,51
system control panel (of the system console)
customer-engineer-control section 248
operator-control section 243
system indication 247
system-reset key 247
system status (from wait, manual, and system indicators) 248
table
manipulation 64
page 60 segment 59
translation 60 termination method of ending instruction execution 74
of channel program 222
of I/O operations (see conclusion of I/O operations) TEST AND SET (TS) instruction 144 TEST CHANNEL (TCH) instruction 207 test indicator 247 TEST I/O (TIO) instruction 208 TEST UNDER MASK (TM) instruction 145
example 303 thermal/CB power check indication 247
TIC (transfer in channel) I/O command 221
time-of-day (TOD) clock 46 key 247
power-on reset 53
states of 46
sync-check external interruption 87
sync control bit 47
synchronization of 101,47 timeout, channel 188
timer, CPU 48
timer damage (machine-check interruption condition) 179,175
timer, interval 49
external interruption 86
updating 49
timing facilities (see CPU timer, clock comparator, interval timer,
and time-of-day clock)
timing facility damage (machine-check interruption
condition) 179,175
TLB (translation lookaside buffer) 64 TOD dock (see time-of-day clock) TOD dock key 247
transfer in channel (TIC) I/O command 221
TRANSLATE (TR) instruction 145
example 303 TRANSLATE AND TEST (TR T) instruction 145
example 304 translation 60 exception address in main storage 79
lookaside buffer (TLB) 64
mode bit in PSW 33
process 61
326 System/370 Principles of Operation
translation (continued)
specification exception 79
table entries, states of 65
table modification 66
tables 59
(see also dynamic address translation)
two's complement, use of in fixed-point operations 116, 289
type of termination (in limited channel logout) 241
types of channels 188
types of (storage) addresses 62
unit
check (I/O unit status condition) 232
deletion (machine-check handling) 172
exception (I/O unit status condition) 233
of information (the byte), basic 14
of operation 74
unit status, I/O conditions 229,237
validity flag 241
unnormalized floating-point operation 159 UNPACK (UNPK) instruction 146
example 305 update (type of storage operand reference) 25
use of translation lookaside buffer 65
valid CBC 172
validation
of keys in storage 173
of registers 173
of storage 173
validity bits (in machine-check interruption code) 180 variable field length of operands 14
virtual
address 57
storage 57
volatile main storage 14
wait indicator 248
wait/running CPU state 30 bit in PSW, BC mode 34
bit in PSW, EC mode 35
warning
machine-check interruption condition 179, 175
mask bit 182
word (definition) 14
word-concurrent fetch 27
working (state of I/O system) 192
working device, effect of reset on 195
wraparound of main storage addressing 14
wraparound of register addresses in LOAD MULTIPLE 132
write command, I/O 2i8
WRITE DIRECT (WRD) instruction 114
X field of an instruction 20 ZERO AND ADD (ZAP) instruction 155
example 309 zone and sign codes in decimal operands 147, 148

/ Technical Newsletter This Newsletter No. GN22-0498 Date September 1, 1975
Base Publication No. GA22-7000-4 File No. S/370-01 Previous Newsletters None
IBM System/370 Principles of Operation
©IBM Corp. 1970, 1972, 1973, 1974
This Technical Newsletter provides replacement pages for the subject publication.
Pages to be inserted and/or removed are:
Title Page, Back of Title Page
Preface, Back of Preface
v through viii
15, 16
47,48
59 (text rearrangement only), 60 63 through 66 (text rearrangement only)
67 (text rearrangement only), 68
69, 70 81, 82 (text rearrangment only, both pages)
83 (text rearrangement only), 84
87, 88 (text rearrangement only)
89, 90 (text rearrangement only)
91 (text rearrangement only), 92
93, blank
95,96
119 through 122
125, 126 (text rearrangement only) 129,130 133,134
145, 146
163,164
175 (text rearrangement only), 176
183, blank 205,206 227,228
241, 242 (text rearrangement only)
249, 250 (text rearrangement only)
271 through 274
311 through 326
All pages to which a change has been made carry a revision notice in the upper margin.
A change to the text or to an illustration is indicated by a vertical line to the left of the
change.
Summary of Amendments
This newsletter corrects technical errors appearing in text and in figures, clarifies certain
ambiguous presentations, improves figure placement, and eliminates a number of typo­
graphical errors.
Note: Please file this cover letter at the back of the manual to provide a record of changes. IBM Corporation, Product Publications, P.O. Box 390, Poughkeepsie, N.Y. 12602 Printed in U.S.A.