Singer 40 User Manual

3 INSTRUCTION FORMAT
READ AND WRITE INSTRUCTIONS
A Read or Write instruction which addresses a disc drive has the following
characteristics:
• Both the LA-field and the LB-field must be zero.
• The A -field specifies the address of a 100-location segment of memory.
For a Read instruction, the segment is the input area into which the
record will be read. For a Write instruction, the segment is the output
area from which the record will be written.
• The B -field specifies the address of a six-character segment of memory.
The segment contains a six-character disc address (discussed as a
separate topic below) .
• Both the A -field and B -field may be modified by the contents of an
index register if the programmer so desires.
SIX-CHARACTER DISC ADDRESS
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The six-character segment of memory which is pointed to by the B-field of the
Read or Write instruction contains the following pieces of information~
• The disc drive device number (0-9).
• The arm number (0-4; on the Model 40, 0 specifies the top arm; on the
Model 42, 0 specifies the bottom arm).
• The track number (000-199, where 000 specifies the outermost track) .
• The sector number (00-99, where sectors 00-49 are accessed by the
upper head and sectors 50-99 by the lower head).
The format of the six-character disc address is shown in Figure 3-1.
Models 40 and 42 Reference Manual 3-1

Singer 40 Specifications

General

Brand	Singer
Model	40
Category	Storage
Language	English