Device Status Byte For Sio, Tio, And Hio Instructions - Xerox 7250 Reference Manual

Table 7. Overflow and Carry Indicators and Condition Codes (cont.)
Overflow t
Indicator
I/O Instruction
or eCI
TDV
0
x
'/fOlfrr
I
0
1
1
AIO
0
A
'40$7)1
0
1
1
Carr/
Indicator
or eC2
0
1
0
1
0
1
0'
1
Significance
I/o
address recognized and previous operation was not terminated
because of a fau It. '
I/o
address recognized but previous operation was terminated
because of a fault.
tt
Selector lOP busy.
I/O address not recognized.
Normal interrupt condition present (channel end or zero byte count).
Unusual interrupt condition present (fault).
Inval id code.
No
interrupt condition present.
tOverflow and Carry indicators apply to the Xerox 530 and Sigma 3 computers. Condition Codes (CCl and CC2)
apply to the Xerox Sigma 5/6/1/8 computers.
ttDoes not apply to the Xerox 530 and Sigma 3 computers.
Table 8. Device Status Byte for SIO, TIO, and HIO Instructions
Bit
Position Function Value
Significance
0
Interrupt pending
1 Set if an interrupt is pending (issued but not yet acknowledged by an
AIO instruction). The controller continues to transmit data, if speci-
fied, unti I the current operation is completed (all data are transferred
or the operation is terminated due to an error condition), but the con-
troller does not accept a new SIO instruction unti I this interrupt has
been acknowledged. An interrupt is cleared by an Ala or HIO instruc-
tion, or manually by the RESET switch on the computer control panel.
1,2
Device condition Indicates the current device condition:
00 Device ready.
01 Device not operational.
10
Does not apply.
11 Dev i ce busy.
3
Mode
1
This bit is always a 1, indicating automatic mode.
4
Unusual end
1
Set
if
the previous operation terminated due to any of the conditions
listed under "Unusual End Conditions."
18 Status Response
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