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Operation
RRF
READ
WRF
WRITE
Octal Code
OOOlOP
2FOONN
OMMMMM
1st command word
2nd command word
3rd command word
N is the number (1- 16) of 64-word records to be transmitted from disc storage
to core storage. F is the number (0 - 3) of the selected disc file. M is the core
memory address into which the first word of the record is stored. P is the
plug number of the DSU on the controller selector.
00030P
7FOONN
OMMMMM
1st command word
2nd command word
3rd command word
N is the number (1- 16) of 64-word records to be transmitted from core storage
to disc storage.
F is the number (0 - 3) of the selected disc file. M is the
memory location of the first word to be transmitted from core storage to disc
storage. P is the plug number of the DSU on the controller selector.
NOTE: The mnemonics are never used in actual coding. The command words
must be written in octal form.
The sequence for addressing the DSU is to select the DSU to be addressed and position one
of the arms.
The access time varies depending upon the distance the arm must travel to be in
position and upon latency time. After the desired arm is in position, the read/write instructions
may be executed.
POSITION COMMAND WORDS
When the command words are to be executed, it is first necessary to store the three command
words in memory locations 3, 4, and 5. An SEL instruction executes the positioning instructions
(command words).
The third word sent from memory to the controller selects the arm, the arm position, and the
address of the frame or frames to be transferred. Bit positions 14 and 13 of command word 1
1
and bit positions 18- 15 of command word 2 select the arm (0-15) which contains the head or
heads to do the writing or reading.
Bits 14- 9 of command word 3 select the arm position
(0 - 63) involved in the transfer of information.
Bits 8- 2 select the first frame (0 - 95) to be
read or written.
V-37
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