IBM 1620 1 Manual page 63

Table 5. Write Check Errors
I/O Check Switch Position
Output Device Stop
Typewi-iter
1620 halts after printing all characters from
transm i tted record.
Tape Punch
1620 halts as soon as an erroneous character
is punched. Tape does not advance.
Card Punch 1620 halts after core-storage to buffer
storage transfer. Card is not punched.
1311 Disk Storage 1620 halts at the end of a sector, or at the
end of the last sector on a track if a
complete track is being read.
indicator and light. When the Overflow Check switch
is set to
STOP
and the Arithmetic Check indicator is
turned on, the computer halts at the end of the in-
struction being executed. If the Start key is pressed,
the Arithmetic Check indicator remains on, and the
computer continues to execute instructions in the
automatic mode, until another overflow occurs.
When the Overflow Check switch is set to
PROGRAM,
and the Arithmetic Check indicator is turned on, the
machine continues to operate in the automatic mode.
The indicator can be interrogated and turned off by
the program.
Console Program Switches
The modifier switches in this group, labeled
PROGRAM
SWITCHES
on the console, are numbered 1 through 4.
A branch occurs when a switch specified by a Branch
Indicator instruction is set to
ON.
When the switch specified is set to
OFF,
no branch
occurs from the Branch Indicator instruction, and the
next instruction in sequence is executed.
When a Branch No Indicator instruction is used to
interrogate one of these switches, the branch occurs
when the switch is set to
OFF.
Register Display Indicators and Switches
The console panel displays the contents of registers
by small incandescent lights that represent the bits
present in each digit of a register (Figure 54). Each
light, representing a particular bit position, is on only
when its corresponding bit is present in the digit
displayed.
Afemory Buffer Register (MBR). The two stored
digits affected by a core storage address are displayed
in the
MBR.
When the core storage location addressed
for display is an even-numbered adress, the digit at
this location is placed in the
MBR
display in the E
Program
Output operation is completed and 1620 can
branch to an error subroutine.
1620 halts as soon as an erroneous character is
punched. T ape does not advance.
Output operation is completed and 1620 can
branch to an error subroutine.
Same as above.
( even) line; the 0 (odd) line contains the digit in
the next higher-numbered location. If the core stor-
age location addressed for display is an odd-number-
ed address, the digit at this location is placed in the
MBR
display on the 0 line; the E line contains the
digit in the next lower-numbered location. When the
machine is in alphameric mode, the complete two-
digit representation of an alphameric character may
be viewed at one time.
Afemory Data Register (MDR). One line of six indi-
cator lights displays the bit configuration of each
digit in core storage as it is read out. These digits
can be seen on single-cycle operation, using the 1620
console
SCE
key. The digit displayed in the
MDR
dis-
play is duplicated in the
MBR-E
or
MBR-O
display, de-
pending on whether the digit read out is located
at an even-numbered or an odd-numbered core stor-
age location.
Operation (Op) Register. Two lines, each with five
lights, display the bit configuration of the two digits
representing the operation code of the instruction
last executed. Flag bits of these two digits are not
displayed.
Digit and Branch. Two lines, each with five lights,
display the contents of the Digit and Branch Register.
This register serves a dual purpose jn the 1620:
1. It decodes the Qs and Q!l digits of Branch
Indicator, Branch No Indicator, and Input/
Output instructions.
2. It temporarily stoTes digits affecting
MARS
(Memory Address Register Storage) during all
I cycles, and stores partial product digits
during multiplication.
Multiplier / Quotient. This five-light register display
shows each multiplier digit as it is used during a mul-
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