Input/Output Control Block (IOCB)

Field Subfield Description
00 Interface Type
0 = MLI interface
1 = IPI Interface
2-F = Reserved
01 IOP Variant Extension (Presently zero)
02-03 IOP Variant. Setup by software, used unmodified by the IOS
02 3 = Inhibit Data Transfer to memory
2 = Backwards Read
1 = ASCII Translation
0 = Real Time
03 3 = Reserved
2 = Reserved
1 = Bypass I/O complete Queue (Software polls IOP R/D for completion)
0 = Conditional Cancel Flag
04-13 Buffer Begin Address.
Absolute Value
Used and modified by IOS
Content not guaranteed at I/O complete.
May be Set by CIO
14-23 Buffer Size
Number of digits to transfer by IOS
Initial Value Only.
24-27 IOP Accumulated R/D. Compatibility Notes A.64
28-31 Remaining Data Length & R/D Field Offset.
Offset relative to current IOCB begin address.
32-33 Reserved
34-39 Buffer MAST Number
Memory Area nailed by CIO
Not used by IOS.
Used by IOC to unnail Memory Area
40-43 Special R/D
Used by software only
Valid only if Bypass I/O complete queue bit set in IOP Variant
Value “8000” = I/O completed.
Value “0000” = I/O not completed.
44-45 Unit Number Compatibility Notes A.64
46-49 Channel Number
Where the DLP command is sent
Set by Software
See Compatibility Notes A.24
50-NN DLP Command or I/O Op Code
MLI: NN=69
IPI: To Be Specified
Built by software
Set unmodified by IOS to DLP except for Unconditional Cancel
MM-PP Remaining Data Length and Result Descriptors
MLI: MM=70, PP=107
IPI: To be specified
Used and modified by IOS
Content guaranteed at I/O complete

DLP Command (MLI Interface)

Field Subfield Description
50-69 DLP Command - MLI Interface
50 DLP Op Code
C = Unconditional Cancel
8 = Read
4 = Write
2 = Test
1 = Echo
51-53 DLP Variants
54-61 Peripheral Device Information
Formerly known as the C-Address
62-69 Peripheral Device Information Extension
Number of bytes (Buffer Size divided by two) in binary to be transfered to the device

IOCB Results Section

Field Subfield Description
70-107 Remaining Data Length and Result Descriptors - MLI Interface
Only current I/O operation relevent field updated by hardware
70-79 Remaining Data Length
Number of digits not transferred
Used and updated by IOS
Content guaranteed at I/O Complete
May be set by CIO
80-83 IOP R/D Compatibility Notes A.64
84-91 DTM R/D Compatibility Notes A.64
92-107 DLP R/D

The remainder of the IOCB is reserved for software use.

processor_state/iocb.txt · Last modified: 2009/05/11 08:35 by scott
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