Page of GA22-7000-4 Revised September 1, 1975
By TNL: GN22-0498
device
addressing, I/O 192
validity flag 241
description 18
end (I/O unit status condition) 232
error, I/O 197
general information 186
not operational (I/O system state) 193
working % system state) 193 (sa also I/O devices and control units) DIAGNOSE instruction 103 digit, decimal 147
digit selector in editing 150 direct-control facility 46
disabling, enabling interruptions 70 displacement (in operand designation) 20 display-and-enter controls 245
DIVIDE (DDR, DD, DER, DE) instruction 163
DIVIDE (DR, D) instruction 128
example 296
DIVIDE DECIMAL (DP) instruction 149
example 306 doubleword (definition) 14
doubleword-concurrent fetch 27
dynamic address translation 57
addresses translated 62
addressing exception during 61,68
control 58
control register 0 58
control register 1 59
exceptions 68, 81
page-translation exception 79, 62
segment-translation exception 79,61
translation-specification exception 79,62
formats, summary 68
page invalid bit 60 page size 59
page table
address 60 entry 60 entry fetch sequence 24
length 60 lookup '61 process 60 segment invalid bit 60 segment size 59
segment table
address 59
entry 59
entry fetch sequence 24
length 59
lookup 61
states of translation-table entries 65
table entries
active 66
attached 65
valid 65
tables 59
modification of 66
translation lookaside buffer 65
EBClDIC chart (see Appendix H)
EDIT AND MARK (EDMK) instruction 152
example 307 318 System/370 Principles of Operation EDIT (ED) instruction 150 example 306 emergency-pull switch 245
emergency signal
external interruption 87
order 97
enable-system-clear key 245
enabling and disabUng interruptions 70 ending of instruction execution, methods of 74
equipment check (sense data) 220 status bit 99
error
program, handling of 75
state of time-of-day clock 46
storage
corrected bit 180 key in storage 180 uncorrected bit 180 error checking and correction (ECC), redundancy correction 172
event mask for program event recording 40 events, interruption causing 80 exception conditions
during decimal operations 149
during EXECUTE operations 129
during fixed-point operations 116
during floating-point operations 161
exceptions associated withPSW 35
excess-64 binary notation 157 EXCLUSIVE OR (XR, X, XI,XC) instruction 128
example 297
EXECUTE (EX) instruction 129
example 298
exceptions during execution 129
execute exceptioJ;l 76
execution, program 19
exigent machine-check interruption conditions
definition of 175
handling of (interruption action) 175, 177
explicit (address) translation 60 exponent
in a floating-point number 157
overflow exception 78
underflow exception 79
extended control mode (EC) 32 PSW format 34
extended-floating-point number 158
extended logout (see machine-check extended logout)
extended logout pointer, I/O 240 external-call
external interruption 87
order 97
pending, status bit 99
external damage, machine-check interruption condition 179, 175
report mask 182
external interruption 84
clock comparator 87
CPU timer 88
emergency signal 87
external call 88
external signal 86
identification in main storage 90 interrupt key 86
interval timer 86
malfunction alert 86

external interruption (continued)
mask (BC mode) 34
mask (EC mode) 34
time-of-day clock sync check 88
external signal, interruption 87
mask bit (in control register 0) 87
failing-storage address
in machine-check extended interruption information 177
in machine-check interruption code validity bits 180 features, System/370 (see Appendix A)
fetch protection bit (see also storage protection) 38
fetch reference, storage operand 25
field (see instruction format)
field validity flags (in limited channel logout) 241
fill character 151
fixed-length operands 14
fixed logout (see machine-check fixed logout)
fixed-point
divide exception 78
exceptions 78
number representation 116
overflow exception 78
flag in CCW
as defined for each type of command 217
chain command 211
chain data 211
program-controlled interruption (PCI) 211
skip 211
suppress-length indication (SLI) 211
floa ting-poin t
divide exception 161, 79
instructions 157, 290 data format 157
examples 309 exceptions 159, 79
number representation 159
register 16
register valid bit (in machine-check interruption code) 180 register save area (machine-check extended interruption
information) 178
format
data 14
dynamic address translation 68
information 14
instruction 20 1/ 0 instruction 197
summary (see Appendix D)
word 14
formation of the real address 62
forming the operand address 21
fraction in floating-point operands 157
functions that differ from System/360 (see Appendix B)
general instructions 116
data formats 116
representation of fixed-point numbers 116
general-purpose design of System/370 9
general register 16
coupled 16
save area (machine-check extended interruption
information) 178
valid bit (machine-check interruption code) 180 general-register-alteration program event 43
guard digit, floating-point 158 Page of GA22-7000-4 Revised September 1, 1975
By TNL: GN22-0498
halfword (definition) 14
HALT DEVICE (HDV) instruction 199
HALT I/O (HIO) instruction 202 HALVE (HDR, HER) instruction 164
handling of access exceptions, 81
handling of (storage) addresses 63
hardware checkpoint (in CPU retry) 172
hardware instruction retry (see CPU retry)
hexadecimal tables (see Appendix G)
I field in an instruction 19
IDAW (indirect data address word) 216
identification of source of interruption 70 identity of storage control unit (SCU), in limited channel
logout 240 immediate operand 20,19 immediate operation (I/O) 222 IMPL (initial microprogram load) controls 245
implicit (address) translation 60 implied field length of operands 14
inadvertent resetting of sense data (see unit check programming
note) 233
incorrect length, channel status condition 233
index (in operand designation) 20 indirect data address (IDA) 190,216
flag (in CCW) 211
word (lDAW) 216
information
formats 14
positioning 15
initial-CPU-reset order 98
initial-micro program-load (lMPL) controls 245
order 98
initial program load (lPL) 54
initial-program-reset order 97
input/ output
address, in limited channel logout 242
commands 217
communications area (IOCA) 239
device 186
addressing 192
attachment of 186
error 197
devices and control units 186
error alert, in limited channel logout 241
extended logout control bit (in control register 14) 182
extended logout pointer 240 general description 17
instructions 197
interface 17
interruption 226, 73
channel available (CAl) 227
channel mask 88
conditions 226
priority of 227
program-controlled (PCI) 233
mask
Be mode (see extended control mode) 33
EC mode 34
operations 185
blocking of data 210 chaining 213
conclusion (termination) due to equipment
malfunction 226
Index 319