Channel Status Byte - RCA 70/46 Reference Manual

Channel Status Byte
(Cont'd)
I nputjOutput Operation
the condition code indicates that Status is stored. The bit significance of
the channel status byte is as follows:
Bit Position 8 is the program controlled interrupt bit. When set, this
bit indicates that a Channel Command Word was accessed which had the
program controlled interrupt flag bit set. A channel interrupt occurs for
the appropriate channel while the input/output operation specified by the
Channel Command Word is being executed.
Note: The program controlled channel interrupt occurs after the first
data byte has been transferred.
Bit Position
9
is the incorrect length bit. When set, this bit indicates
that when the input/output operation was terminated, the byte count
specified in the channel command was not equal to the number of bytes
received from, or sent to, the input/output device. The incorrect length
indicator can be set only if the suppress length indicator flag bit in the
channel command word is reset to
o.
The following conditions cause the incorrect length bit to be set:
1. Count High on Input (Read, Read Reverse, Sense). The main
memory area specified by the Channel Command Word is not com-
pletely filled by transmission from the device. The final byte count
in Channel Command Register-II is greater than zero.
2. Count High on Output (Write, Write Control). Data in the main
memory area specified by the Channel Command Word is not com-
pletely transferred and the device terminated. The final byte count
in Channel Command Register-II is greater than zero.
Notes:
1. If incorrect length occurs during command chaining and the
Suppress Length Indicator flag bit of the current command is reset,
the incorrect length bit is set.
2. If incorrect length occurs during the last command of a chain (the
Chain Data flag bit is reset), and the Suppress Length Indicator
flag of the command is set, the incorrect length bit is not set.
Bit Position
10
is the program check bit. When set, this bit indicates
that a programming error was detected by the channel.
The following conditions cause the program check bit to be set:
1. Invalid Channel Command Word Address. The addressed Channel
Command Word is not located on a double word boundary.
2. Invalid Channel Command Word Address. The addressed Channel
Command Word is outside the available main memory for the par-
ticular installation.
3. Invalid Data Address. The main memory location specified by the
data address in the Channel Command Word is outside the avail-
able main memory for the particular installation.
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