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Section 5: Error Recovery Procedures
The 3803/3420 error recovery procedures (ERPs) provide uniform minimum
recovery actions independent of operating systems or equipment and describe
additional recovery options.
An
1/0
error causes an interrupt and sets an error indicator in the channel status
word.
If
Interface Control Check (bit 46) or Channel Control Check (bit 45) is
indicated in the csw, perform "Terminal Action lb."
If
Unit Check (bit 38) is
indicated in the csw, execute a Sense command to further define the error
before selecting the tape control. Figure 11 shows checking sequence
("priority") for status and sense bits, and indicates the actions required.
Sense
Applicable To:
Byte
Status
Priority
Bit
Byte
Bit
Bit Condition
Read
Write
Control Action
01
38
Unit Check
x
x
x
II
02
0
3
Equipment Check
x
x
x
x
03
0
2
Bus Out Check
x
x
x
IV
04
0
1
Intervention Required
x
x
x
Ill
05
0
0
Command Reject
x
x
x
XIII
06
0
5
Overrun
x
x
VII
07
1
4
Load Point
x
x
XII
08
0
4
Data Check
x
v
08
0
4
Data Check
x
VI
08
0
4
Data Check
x
VIII
09
7
4
Data Security Erase
x
XI
10
44
Channel Data -Check
x
x
x
VII
11
0
7
Data Converter Check
x
XIII
12
1
7
Not Capable .
x
x
x
IX
13
5
3
ID Burst Check
x
XIV
14
No Previous Sense Bits
x
x
x
x
On
15
47
Chaining Check
x
VII
16
42
Program Check
x
x
XII
17
43
Protection Check
x
x
XII
18
41
Incorrect Length
x
x
XII
Figure 11. Status and Sense Indicator (Bits) Checking Sequence
Section 5: Error Recovery Procedures
51
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