Condition Codes - Xerox 7250 Reference Manual

MEMORY
Disk
I/o
program
Interrupt Machine fault
routine routine
SIO
AIO Read Direct
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I/o
Command Doubleword
l
"Order
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Memory byte address
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I/O Table -
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1
Second de ta
Third data
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Fourth data
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byte byte
byte byte
0
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' . ' S ' 6 i 1.'"lQl'21111"l: ol? ' 1 " 1 0 ) '
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Data byte
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Data byte
Data byte ILast data byte/
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11. 11 I) : .. IS 10 ;, " I. 20 2' 22 21,2' 15 26 27 <1Il
:;>9 )(I
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SIO Instruction
II
Operation
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r - - -
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lOP
lOP Subchannel
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r--
t
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CONTROLLER
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--
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11
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5 1 i ,12 5,
Order In Status Device Status Byte Condition Codes
Address Register
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I
Track Sector
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I
I
DRIVE
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CPU
General register 0
1
0000
First command
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0000
0000 0000
doubleword address
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Register R
STATUS RESPONSE
1
0000 0000 0000 0000
Current command I
doubleword address
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,
.
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'0 II Ij ) 1 . ' 5
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18 1 ~ l' ~. J, ~ •
20
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Register Rul
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Operational
Dev
I
ce Status Status
Byte count
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0 1 1 1 .
s.,
8
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20
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Condition Codes
- [ill
c (
' z
--
Legend
Each disk has a unique device address. CPU executes instructi
ens;
lOP executes commands; and the controller and device execute
orders.
~
X'Ol' Write
X'02' Read
X'03' Seek
X'04' Sense
X'05'
Check-write
X'I2'
Read
X'13' Test
I/O Command Doubleword
Memory byte address
Pointer to the first byte
DC Data chaining flag
IZE Interrupt at zero byte count
CC Command chaining flag
ICE Interrupt at channel end
HTE
Halt on transmission error
IUE
Interrupt at unusual end
SIL Suppress incorrect length
S Skip
Byte count Number of bytes to
be
transmitted
SIO instruction
I
R General register that is to contain the
first word of the status response
DC and D
Device controller and device oddresses
Register 0 Pointer to the first commornjdoublew
Status Reseonse, Program may request a 2-word or a I_ord
status response, or none.
Current command doubleword address: pointer to the cumtnt
doubleword in the command list.
Device Status: Reports condition of the device and controller
such as not operational, ready, busy.
I
Operational Status (Order In Statu,): Reports tronsmi"ion err
or,
incorrect length, channel end, and unusual end.
Byte count: number of bytes yet to be transmitted.
Condition Codes. eCI and CC2 report, e.g., oddress recog-
nized, I/O instruction accepted or nat accepted.
Address Register. Seek order initially sets track and sector
addresses. Controller automatically increments.
Figure 6. 1/0 Operational Flow - Xerox Sigma 5/6/7/8
8 1/0 Operational Flow