Page of GA22-70004 Revised September 1, 1975
By TNL: GN22-0498
malfunction-alert external interruption 86,175
malfunction (selective) reset in I/O system 195 indicator 246
manual operation of system (see system console)
mask (in BC mode PSW) channel 33 33 I/O 33
maGhine-check 34
program 34
masks (in EC mode PSW) external 34
inplllt/output 34 maGhine check 35
program 35
program-event recording 34
mask bit in control of interruptions 71
mask position values used in BRANCH ON CONDITION 121
masks, monitor 39
MCEL (see machine-check extended logout)
microprogram controls, initial 245
mode
BC (basic control) 32
control bit in PSW 34
EC (extended control) 32 \
of channel operation (data transfer) 188
modifier bits in CCW command code 212 MONITOR CALL (MC) instruction 132
monitoring 39
class number 39,91
code 39,91
inte:rruption identification (see monitor class number;
monitor code) 91 masks (in control register 8) 39 MOVE (MVC, MVI) instruction 133
example 299 MOVE LONG (MVCL) instruction 133 MOVE NUMERICS (MVN) instruction 135
example 300 MOVE WITH OFFSET (MVO) instruction 135
example 300 MOVE ZONES (MVZ) instruction 136
example 300 multiple PCI interruptions (see programming notes) 221 multiple simultaneous interruption requests (see priority of
interruptions) 89
multipllexer channel (see byte-multiplexer channel and
block-multiplexer channel)
MULTllPLY (MDR, MD, MER, ME) instruction 167
MULTllPL Y (MR, M) instruction 136
example 301 MULT1[PL Y (MXD, MXDR) instruction 167 MULTIPLY (MXR) instruction 167 MULTIPLY DECIMAL (MP) instruction 153
example 307 MULTIPLY HALFWORD (MH) instruction 136
example 301 multiprocessing 95, 9
exam pIes 310 near valid CBC 171
no-ope:ration control command 219
non shared subchannel 189
nonvolatile main storage 14
normal sequential instruction execution 22
normalization in floating-point arithmetic 159
322 System/370 Principles of Operation
not operational (state of I/O system) 192
not ready status bit 100 nullification (method of ending instruction execution) 74
number representation
decimal 148
fixed-point 116
with two's complement 289
floating-point 159
numbering
bits of a byte 14
byte locations in main storage 14
numerics 147
one's complement, use of in fiJted-point operations 117
op code (operation code) 20 operand field length 14
operands
address specification of 19
immediate 20 in main storage 20 in registers 20 storage 25
fetch reference 25
relation between references 27
store reference 25
update reference 26
operating state 30 operation code (of an instruction) 20 operation exception 76
operation, I/O 186, 17
operation, unit of 74
operational (I/O state) 192
operator-intervening status bit 99
operator section (of system control panel) 243 OR (OR, 0, 01, OC) instruction 137
example 301 order
conditions determining response to 98 I/O (definition) 189
signaling and response 97
order-code interpretation, conditions precluding 98
organization, system 13
overflow
decimal 147
exponent 158
fixed-point (see ADD (AR» 117
overlap, destructive (in MOVE LONG) 133
overlapped fields, decimal 147
overrun (sense data) 220 PACK (PACK) instruction 137
example 302 packed decimal number 147
page 58
address 60 index field 58
invalid bit 60 size bits (in control register 0) 58
table 60 address 60 entries 60 entry format 60 length 60 lookup 61
page-translation exception 79
parity bit 171

pattern character 150 PCI (see program-controlled interruption) PER (see program-event recording) PER events
with concurrent exceptions 45
with dynamic address translation 42
with interruptible instruction 42
with LOAD PSW 41
with SUPERVISOR CALL 40 point of interruption (interruptions) 74
point of interruption (machine-check interruption) 176
postnormalization 159
power check indication, thermal/CB 247
power-off key 246
power-on key 246
power-on reset CPU 53
main storage, effect of on 53 TOD (time-of-day) clock 53
powers of two, table (see Appendix F)
prefixing 95, 14
prenormalization 159
priority
of access exceptions 84
of clock comparator interruptions 86
of CPU timer interruptions 86
of exigent machine-check interruptions 89
of external interruptions 86
of interrupt key interruptions 86
of interval timer interruptions 86
of I/O interruptions 227, 89
of program exceptions 85
table of program exceptions 85
privileged
instruction 30 operation exception 76
problem state 30 processor address (stored by external interruption) Jl/;'O program
check (channel status condition) 234
execution 19
interruption 75
identification in main storage 90 program-controlled interruption (PCI) 215
channel status condition 233
flag (in CCW) 211
program-event recording (PER) 39,80 address in main storage 41
code 41
control register allocation 40 event masks 40 general-register-alteration m:asks 40 indication of events concurrently with other interruption
conditions 43
interruption identification in main storage 90 mask, EC mode 34
operation 40 starting/ending address 40 storage area designation 42
program events 42
general register alteration 43
indication of 45
instruction fetching 42
storage (main) alteration 42
successful branching 42
program execution 19 Page of GA22-70004 Revised September 1, 1975
By TNL: GN22-0498
program-interruption conditions
access exception, recognition of 80 addressing exception 76
data exception 78
decimal-divide exception 78
decimal-overflow exception 78
execute exception 76
exponent-overflow exception 78
exponent-underflow exception 79
fixed-point divide exception 78
fixed-point overflow exception 78
floating-point divide exception 79
monitor event 80 operation 75
page-translation 79
priority of 85
privileged operation 76
program event 80 segment-translation 79
significance 79
special operation 80 specification 77
table of priorities of 85
translation specification 79
program mask and condition code validity bit (in machine-check
interruption code) 180 program mask in PSW BC mode 34
EC mode 35
program-reset
initial 52
order 97
program state (see CPU state)
program status word (see PSW) protection check (channel status condition) 234
protection exception 76
summary table 77
protection key
in CAW 210 in CSW 228,236
protection key in PSW BC mode 33
EC mode 34
protection, storage (see storage protection) PSW (program status word) 32, 22 PSW, BC mode format 33
channel mask 33
condition code 34
current 16
extended-control (EC) mode 34
external mask 33
ILC (instruction-length code) 34
instruction address 34
interruption code 34 I/O mask 33
machine-check mask 34
problem state bit 34
program mask 34
protection key 34
wait state bit 34 PSW, EC mode format 33
condition code 35
EC mode bit 34
external mask 34
instruction address 35 I/O mask 34
Index 323