Sense - IBM 7074 General Information Manual

Reactivation of the inoperative access unit is ac-
complished manually by the customer engineer after
the fault has been corrected.
Prepare to Verify, Track with Addresses (DVTA-88)
This order, followed by a read or write command,
permits the reading or writing of a full track of infor-
mation, including record addresses and records. It
makes use of the home address that defines the track
address.
This order instructs the file control to do the fol-
lowing.
1. Select the desired module and access mechanism.
2. Supply the home address to be verified.
3. Condition the file control to operate on a full-
track basis and receive and transmit both record
addresses and record areas in response to a sub-
sequent read or write command.
The order is used whenever changes are to be made
to record addresses and insertions, or deletions are to
be made on a track that contains randomly distributed
records.
The execution of this order is similar to that per-
formed by the prepare to verify (cylinder operation)
in that only the home address is verified. If verifica-
tion is successful, reading or writing will begin at the
following record address and continue through the
records and the record addresses until the computer
signals
STOP
or the file control recognizes the end of
format area. Non-verification of the home address re-
sults in an
UNUSUAL END
signal with no transmission of
data to or from the disk storage.
Prepare to Verify, Home Address (DVHA-89)
This order prepares the file control to read or write
an entire track of data and addresses including the
home address identifier. The home address must be
supplied for subsequent verification. For execution of
this order, the home address switch must be on. (The
switch is located on the 7631.)
This operation is terminated by a
STOP
signal from
the computer or when the file control recognizes the
index point.
Sense
The sense command instructs the file control to trans-
mit status data to the computer to indicate error and
unusual conditions as well as attention conditions.
This operation is similar to a read command except
that only the ten 4-bit characters are transmitted to
12
the computer. The status data are transmitted to the
data channel of the using system over the
BCD
A, 4, 2,
and 1 bit lines. From the data channel, the 4-bit char-
acters are converted to either the
BCD
6-bit character
(7080 and 7090) or the two-of-five code (7070/7074),
and sent to the computer.
Status data are set in bit form for each read, write,
and control operation performed by the file control
and are available to the computer by means of the
sense command. The status data should be called for
by the computer before the initiation of the next read,
write, or control command. (The initiation of the next
command resets all error indications of the status
data. )
Figure 9 shows the make-up of the status data trans-
mitted to the data channel of the using system.
Status character 0 summarizes the type of check or
condition. Characters 1 and 2 give the type of check
encountered. (Invalid address check has been added.)
Character 3 gives the different, exceptional conditions;
character 4 gives the data mode; characters 5, 6, and
7 give attention conditions; and characters 8 and 9
are reserved.
Status Bit BCD
Assignment
Comment
Char
No.
Bit
0 3 A Reserved
5
4
Program Check Summary
6 2 Data Check
Byte
7 1 Exceptional Condition
1 3
A
Invalid Sequence
5
4
Inval id Code Program
6 2 Format Check
Check
7 1 No Record Found
2 3
A
Inval id Address
5 4
~spoose
Check- -
- - -
6 2 Data Compare Check
Data Check
7 1 Parity or Check Char Code Check
3 3 A Access Inoperative
5 4 Access Note Ready Exceptional
6 2 Disk Storage Circuit Check Condition
7 1 File Control Circuit Check
4
3 A Reserved
5
4 Six-Bit Mode
Data Mode
6 2 Reserved
7
1 Reserved
5
3 A Module 0
5
4
Module 1
6 2 Module 2
7 1 Module 3
6
3 A Module 4
5 4 Module 5
Attention
6
2 Module 6
7 1 Module 7
7 3
A
Module 8
5
4 Module 9
6 2 Reserved.
7 1 Reserved
8,9 Reserved
Figure 9. Status Data Bit Assignment