Xerox 550 User Manual

INPUT jOUTPUT INSTRUCTIONS
The I/O instruction set is comprised of eight instructions,
as listed
below.
Instruction Name
Mnemonic
Start Input/Output
SIO
Test Input/Output
TIO
Test Device
TDY
Halt Input/Output
HIO
Reset Input/Output
RIO
Poll
Processor
POLP
Poll
and Reset Processor POLR
Acknowl edge Input/Output Interrupt
AIO
OVERALL CHARACTERISTICS
All I/O instructions are privi leged and can be performed
only when the basic processor (BP) is in either the master
or master-protected mode. If the BP attempts to execute
an I/o instruction when it is in the slave mode (bit 8 of
the current PSW is a 1), the instruction is aborted at the
time the operation code is decoded and the BP traps to lo-
cation X
'
40
'
•
Programs operating in the slave mode must
request I/O services from the System Monitor.
At the end of every I/O instruction, the condition code
bits represent a summary description of the results of the
I/O operation and conditions within the addressed I/O
subsystem. Specific condition code settings and meanings
(unique for
each I/O instruction) are contained in the de-
tailed description for each I/o instruction.
All I/O instructions, except RIO, may request detailed
I/O status information. The type and amount of I/O status
information that may be requested is determined by the op-
eration code and the R field of the I/O instruction. The
R
field also designates which general register{s) is to be
loaded with the requested information. (Refer to I/O Status
Informati on for further detai Is. )
I/O instructions are similar to other word-addressing in-
structions in that bits 15-31 may be modified by indirect
addressing and/or indexing. However, the final value of
the~e bits is r.ct used as en effect;vc \ditua! addieSS for
memory reference. Instead, depending upon the I/o in-
structi on, these bi ts are used as an extensi on to the opera-
tion code field, as an I/O address to select a particular
I/O subsystem, or they may be reserved. Further detai Is
of I/O instructions are illustrated in Figure 13 and de-
scribed in Table 13.
110 Input/Output Instructions
1/0 STATUS INFORMATION
SIO, TIO, TDY, AND HIO INSTRUCTIONS
If the R field is coded with a 0, no status information is re-
quested nor loaded. If the R field is odd, one word of status
information is requested to
be loaded into register R as spec-
ified by the R field. If the R field is even (not zero), two
words
of status information are requested to be loaded into
registers
Rand Ru 1.
The following I/O status information may be loaded into
register R only when the R field is coded with an even
(nonzero) value.
The significance of each bit within register R is described
in Table 14.
The following
I/O status information may be loaded into
register R if the R field is odd, or into register Ru 1 if the
R field is even and not zero.
The format of information within the specified general reg-
ister (R or Ru1) is shown below.
Device Status Byte. These eight bits (0-7) when loaded
into the specified general register provide status information
pertaining to the addressed device and device controller or
lOP. The significance of each bit when requested by an
SIO, TIO, and HIO instruction is described in Table 15.
The significance of these bits when requested by a TDY in-
struction is different and is described in the applicable
peripheral device reference manual.
Operational Status Byte. Bits 8-15 of the specified gen-
eral register (R or Ru1) indicate either the presence (1) or
absence (0) of various errors which may have occurred
during an I/o operation. The significance of the individ-
ual bits within the operational status byte are described
in Table 16.
Table 17 is the summary description of the Device Status
Byte
and the Operational Status Byte.
Byte
Count. Bits 16-31 of register Ru1 indicate the num-
ber of bytes that have to be transmitted to or from mem-
ory in
the operation called for by the current I/o command
doub
I eword •
RIO INSTRUCTION
No status information is returned to the general registers
for
an RIO instruction (the R field is ignored). Only con-
dition code bits (CCl - CC3) are set to reflect the I/o
condi ti ons.

Xerox 550 Specifications

General

Brand	Xerox
Model	550
Category	Printer
Language	English