RCA 70/46 Reference Manual page 120

Halt Device
(HDV)
General Description
Format
(SI)
Condition Code
Interrupt Action
Notes
Privileged
In8tructions
• The contents of the general register specified by Bl are added to the Dl
field, and the resultant sum identifies the channel to be halted. The channel
is specified by bit positions 21 through 23 of the sum. If a multiplexor is
specified, bit positions 24 through 31 of the sum identify the device to be
halted. The I field is not used and must be zeros. Bufferred devices operating
off-line, and independent of the channel/device control electronics, cannot
be stopped by using this instruction. The condition code specifies the results
of the instruction.
9E
o
7 8 15 16 19 20
31
• 0 -not busy.
1 - standard device byte stored in scratch-pad memory.
2 - termination accepted.
3 - inoperable.
(For a detailed description of the condition code settings, see Notes
below.)
• Privileged operation.
• 1.
The address portion of this instruction specifies the device and
channel as follows:
Bit Positions
Chann.1 Specified
21 22 23
0 0 0
Multiplexor
0 0 1 Selector No. 1
0
1
0
Selector No.2
0
1 1 Selector No. 3
1 0 0 Selector No. 4
1 1 0
Undesignated
Bit positions 24 through 31 specify one of 256 possible devices.
2. If a device operating on a selector channel is to be halted, the device
number does not have to be specified.
3. The channel address word in main memory location 72, the channel
block address in main memory location 76, and the channel command
word are not used by this instruction.
4. A termination interrupt occurs when any input/output operation is
terminated. Status bits are stored in scratch-pad memory when the
termination interrupt occurs.
5. All five flags in CCR-II are cleared if the Halt Device instruction is
accepted. Therefore, upon termination, the incorrect length counter
in the channel status byte is set if the count is not zero.
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