RCA 70/46 Reference Manual page 50

Channel Command
Word (CCW)
(Cont'd)
o
Command
Code
Flags
Input/Output Operation
Address of First Data Byte or Address of
Next CCW if Command is a Transfer in Channel
7 8
Reserved for
Future Expansion
Byte Count
31
32
36 37
47 48
63
Bit Positions
0
through 7 contain the command code, which specifies
the operation to be performed by the I/O device. (See table 10.)
Table 10. Command Code Operations
Command Code Operation
0
1 2
3
4 5
6 7
Bit Position
M
M
M M 0 0 0 1 Sense
M M M M M/O 0 1
0
Read Reverse
M M M M/B M/O 0 1 1 Write
M M M
M/B M/O 1 0
0
Write Erase
M M
M M/B M/O 1 0 1 Read
M M
M M
0
1
1 1
Write Control
M M M M
1 0 0 1 Transfer in Channel
Notes:
1. Any command code other than the ones shown in table 10 is illegal
and must not be programmed. If this rule is violated, the 'resulting
effect on the channel and device is unpredictable. If one of the legal
commands is issued to a device which is not capable of accepting
the operation (i.e., a Write command is issued to a card reader),
the command, after being accepted, is terminated by the device con-
trol electronics. A channel interrupt occurs and the sense byte(s)
indicate the illegal operation.
2. The bit position designated as "B" indicates that the specified device
is connected to the multiplexor channel and the multiplexor is to
be operated in the burst mode. If this position is a 1 bit, the multi-
plexor channel is locked-on to the selected device, and the servicing
of other devices connected to the mUltiplexor channel is inhibited.
A burst mode can only be initiated when it is specified in the first
command of a chain. Subsequent commands, linked by chaining,
cannot initiate a burst mode. However, if the first command in a
chain specifies burst mode, all commands in the chain are executed
under burst mode conditions.
3. Bit positions designated as M (modifier) indicate variations of the
operation and are unique to the specific input/output device.
An explanation of the commands shown in table 10 is as follows:
Sense
(0001) -
Information is transferred from the specified
input/
output device control electronics to main memory. The information trans-
41