RCA 70/46 Reference Manual page 53

Channel Command
Word (CCW)
(Cont'd)
Input/Output Operation
number of bytes sought by, or sent from, the input/output device.
(When a command or chain of commands terminates, the data byte
count has not lapsed.) An example of an incorrect length condition
is a tape read which terminates on a gap before the byte count has
lapsed. If the SLI bit is set, the program does not receive an indica-
tion of an incorrect length upon termination of the input/output
operation. If the SLI bit is reset, the program receives an indication
of an incorrect length upon termination of the input/output opera-
tion. This indication is contained in the channel status byte.
Notes:
1.
If the SLI bit is set and the chain data flag of the final CCW in a
chain is reset, the incorrect length indication is suppressed, if it
occurs.
2. If the chain data flag of a CCW is set and an incorrect length
condition occurs, the program is notified of the condition regardless
of the setting of the SLI flag.
3. Bit position 35 is the Skip flag (SKIP). In conjunction with data
chaining, portions of a block of information can be sup'pressed during
an input operation. If this bit is set, the transfer of data to main
memory specified by this command is suppressed. This bit can be
used only with Read, Read Reverse or Sense commands.
4. Bit position 36 is the Program Controlled Interrupt flag (PCl).
During data and command chaining, the 70/46 Processor has the
ability to notify the program of the progress of chaining through
an interrupt when a channel command word is fetched. When this
bit is set, a channel interrupt occurs when the channel command
word is fetched from main memory and the first data byte has been
transferred. This flag is ineffective if the channel is the multiplexor
operating in burst mode.
5. Bit positions 37 through 47 are reserved for future expansion and
must be set to all zeros by the program.
6. Bit positions 48 through 63 contain the count of the number of
bytes to be transferred
to
or from main memory during the input/
output operation (from 0 to 65,536 bytes). An initial count of zero
specifies the maximum number of bytes
to
be transferred.
The staticizing of 70/46 I/O instructions is subject
to
translation
similar to any other instructions, except for the execution of I/O instruc-
tions data servicing, and interrupts that
utiliz~
direct addresses only,
and are not subject to dynamic translation.
1.
Address of I/O instruction - Translatable
2. I/O instructions staticized address
- Direct
3. Address of CAW
- Direct
4. Address of CCW
- Direct
5. Address of CCB
- Direct
6. Contents of CCW
- Direct
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