Control Data 1700 Reference Manual page 21

60330800 A
4) 800 bpi (A3 1) - Data is recorded at a density of 800 bits per
inch.
5) Select 556 bpi (A4 1) - Data is recorded at a density of 556 bits
per inch.
*
6) Select 200 bpi (A5
1) -
Data is recorded at a density of 200 bits
per inch.
*
7) Assembly/Disassembly Mode (A6
=
1) - In this mode the computer
word consists of 12 or 16 bits which, during a write, are disas-
sembled into two 6-or 8-bit tape words. During a Read, the tape
words are assembled into the original computer word.
8) Tape Unit 0-7 (A9 - 7) - This code matches the Unit Select setting
of the desired transport.
9) Select Tape Unit (A10 = 1) - This code and bits 9- 7 of A select a
tape transport
10) Deselect Tape Unit (All
=
1) - This bit disconnects a tape transport
that is selected and protected, thus allowing an unprotected program
access to the controller. Deselect Tape Unit must be a singular
type function.
Operations Defined by Q and Input to A
Read: A Read operation transfers data from tape to the computer and
checks parity • To perform a Read, load Q with W
=
00, E
=
equipment
number, and D
=
00. An Input to A initiates the transfer of one 6-, 8-, 12-
or 16-bit character to the lower bits of A. **
The controller transfers characters to the computer until the computer (or
converter) stops requesting characters, or until the controller senses the
end of a record. If the computer stops requesting characters, data trans-
fer to the computer stops, but tape motion continues until the end of the
record. If a new Read Motion function is received by the controller before
tape motion stops at the end of a record, motion continues in a non- stop read.
*Not used with 609 Tape Transport.
**If the input is a buffered input via the converter, an Output from A sup-
plies address information to the converter. The converter controls the
buffered operation. The controller loads pach tape word into the buffer
area.
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