IBM 1620 1 Manual page 83

Bit Configuration
Bit Configuration
Digit
C
F 8 4 2 I
0 X
I
X
2
X
3 X
X X
4
X
5
X
X X
6 X
X X
7
X X X
8 X
9 X X
X
Indicator Codes
Code Name
01-04 1620 Program ,Switches 1-4
06 Read Check
07 Write Check
09 Last Card
II High/Positive (H/P)
12
Equal/Zero (E!Z)
13 H/P or E/Z
14 Arithmetic Overflow Check
*15 Exponent Check
16 MBR-E Check
17 MBR-O Check
19 Any Check
*36 Address Check
*37 Wrong-Length Record/
Read-Back Check
*38 Cyl inder Overflow
*39 Any Disk Indicator
*Special Feature
Table Areas in Core Storage
Address
00000-00099
00000-00099
00100-00299
00300-00399
Area
Console Area
Product Area,
Multiply Table
Add Table
Appendix C
1620 Storage Register Functions
IR-l Contains oddress of next instruction if machine is
stopped with Stop key or Halt instruction. Saves
return address when interrupt is serviced.
IR-2 Saves return address when BT and BTM instructions
are executed.
IR-3
IR-4
OR-l
OR-2
OR-3
OR-4
OR-5
PR-I
PR-2
PR-3
MAR
MBR
MDR
OP
CR-l
Contains interrupt address - used in place of IR-l
during interrupt program operation
Saves return address when any Branch and Transmit
instruction is executed in the Interrupt Program (1710
Control System only).
Contains Q address after I cycle of an instruction.
In disk storage operations, used to store and control
disk sector address.
Contains P address after I cycle of an instruction.
In disk storage operations, contains core storage
address where data from disk storage is written to
or read from.
Retains address of low-order multiplier digit during
multiplication.
Used to store and contro I the exponent address Eq
during automatic floating-point operations.
Used to store and control the exponent address Ep
during automatic floating-point operations.
Saves return address when a Save key operation
occurs. Decremented for each new multiplier digit
during multiply.
Decremented for each new multiplicand digit
during multiply.
Used to odd partial product to each multiply cycle
resu It. In disk storage operations, used to store
and control number of sectors in operation.
Addresses core storage.
Receives digits entering or leaving core storage.
Receives addressed digit entering or leaving core
storage.
Contains Op code of instruction just executed if
machine is stopped with Stop key or Halt instruction.
Used to store the algebraic difference between Ep
and Eq for determination of decimal alignment
during automatic floating-point operations.
CR-l is also used during floating-point operations
to count high-order zeros when normalizing- the
contents of CR-l are subtracted from Ep.
Multi pi ier/Q uotient Contains multiplier and quotient
digits during multiply and automatic
divide operations.
Digit and Branch Decodes Q8 and Q9 digits of BI, BNI,
and I/O instructions.
Stores partial product digits during
multiply instructions.
Stores digits affecting MARS during
all I cycles.
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