Xerox Sigma 6 Reference Manual page 94

Bi
t
Posi tion Function
12 lOP memory error: if a memory parity error has
occurred while the lOP was fetching a command,
this bit is set to
1.
Operation is terminated with
an "unusual end".
13 lOP control error: this bit is set to 1 if the lOP
has encountered two successive TRANSFER IN
CHANNEL commands.
14
15
16-31
lOP halt: this bit is set to 1 if the lOP has issued
a halt order to the addressed I/O device because
of an error condition.
Selector lOP busy: this bit is set to 1 if a selector
lOP is addressed by the I/O instruction and the
selector lOP is currently in use by some I/O de-
vice. The selector lOP is considered to be in use
from the time that a device accepts an S10 in-
struction until the operation is completed.
Byte count: a count of the number of bytes yet to
be transmitted to or from memory in the operation
called for by the current command doubleword.
If the R field value of the SIO instruction is even and not
0, the condition code and register R+ 1 contain the informa-
tion described above and register R contains the following
information:
Bit
Position Function
16-31 Current command doubl eword address: the 16
high-order bits of the core memory address from
which the command doubleword for the I/O opera-
tion currently being processed by the addressed
device controller was fetched.
HIO HALT INPUT/OUTPUT
0/Vord index al ignment, privi leged)
HALT IN PUT/OUTPUT causes the addressed device to im-
mediately halt its current operation (perhaps improperly, in
the case of magneti c tape un
j
ts, when the devi.ce is forced to
stop at other than interrecord gap). If the device is in an
interrupt-pending condition, the condition is cleared.
If the R field of the HIO instruction is
a
or if no I/O ad-
dress recognition exists, no general registers are affected,
but the condition code is set. If the R field is an odd
value, the condition code is set and the following informa-
tion is loaded into register R.
I
St~tus
I
Byte
~ount
I
0',
,I." ,",. '""I"""""" ....
I~"""""u"I~~~,,
86 Input/Output Instructions
The status information returned for HIO has the same in-
terpretation as that returned for the instruction SIO and
shows the I/O status at the time
cf
the halt. The count
information shows the number of byies remaining to be
transmitted at the time of the halt. If the R field of HIO
is an even value and not
0,
the condition code is set, reg-
ister R+l is loaded as shown above, and register R contains
the following information:
The current command doubleword address has the same in-
terpretation as that for the instruction SIO.
Affected: (R), (Rul), CC1,CC2
Condition code settings:
2 3
4
o
0
o
Result of HIO
VA
address recognized and device con-
troll er is not "busy
II •
VA
address recognized but device con-
trollerwas "busy"at the time of the halt.
VA
address not recognized.
TlO
TEST INPUT/OUTPUT
0/Vord index alignment, privileged)
TEST INPUT/OUTPUT is used to make an inquiry on the
status of data transmission. The operation of the selected
lOP, device controller, and device are not affected, and
no operations are initiated or terminated by this instruction.
The responses to TIO provide the program with the informa-
tion necessary to determine the current status of the device,
device controller, and lOP, the number of bytes remaining
to be transmitted to or from memory in the operation, and
the present point at which the lOP is operating in the com-
mand list. If the R field of the TIO instruction is 0, or if
CC 1 (as a result of the execution of this instruction) is a 1,
no general registers are affected, but the condition code is
set. If the R field of TIO is an odd value, the condition
code is set and the I/O status and byte count are loaded
into register R as follows:
The status i nformati on has the same i nterpretati on as the
status information returned for the instruction SID and shows
the I/O status at the time of sampling.
The count information shows the number of bytes remaining
to be transmitted at the time of sampling. If the R field of
the TIO instruction is an even value and not 0, the