IBM 1620 1 Manual page 50

Table 4. Summary of Disk Storage Program Instructions
Mode
Op
Q
ll
Instruction Mnemonic
Code
34 1 Seek SK
36 0 Read Disk/WLRC RDGN
Sector
38 0
Write Disk/WLRC WOGN
Mode
36
1
Check Disk/WLRC CDGN
36 4
Read Disk Track/WLRC
RTGN
38 4 Write Disk Track/WLRC WTGN
Track
Mode
36 5 Check Disk Track/WLRC
CTGN
36
2
Read Disk RON
Sector
38
2
Write Disk WON
Mode
36 3 Check Disk CON
36
6 Read Disk Track
RTN
Track
38 6
Write Disk Track
WTN
Mode
36 7
Check Disk Track CTN
has not been decremented to 000, the operation is
terminated and the Cylinder Overflow indicator (38)
is turned on. Therefore, the greatest number of sec-
tors that can be read with one instruction is 200, one
full cylinder.
As each character is read from disk storage, it is
checked for parity. Failure to meet the parity check
causes the Read-Check indicator (06) to be turned
on. The
MBR-E
indicator (16) or the
MBR-O
indicator
(17 is turned on to indicate a parity error in a char-
acter going into core storage. Any parity check will
terminate the operation.
This instruction checks, in addition to sector count,
that the correct number of characters is transferred
from disk storage to core storage. A group mark
46
Operation
Return access mechanism to "home" position and then
move in to cylinder specified.
Transfer data from specified number of disk secton to
core storage. Check length of record.
Transfer data from' core storage to specified number
of disk secton. Check length of record.
Note: The Write Address key must be off.
Compare data in specified number of disk secton with
data in core storage. Check length of record.
Transfer addresses
and
data from the 20 sectors of one
track to core storage. Check length of record.
Transfer address and data from core storage to the 20
sectors of one disk track. Check length of record.
Note: The Write Address key must be on.
Compare addresses
and
data from the 20 secton of a
disk track with addresses and data in core storage.
Check length of record.
Transfer data from specified number of disk sectors
to core storage.
Transfer .data from core storage to specified number
of disk sectors. Note: The Write Address key
must be off.
Compare data from specified number of disk secton
with data in core storage.
Transfer addresses and data from the 20 secton of one
track to core storage.
Transfer addresses
and
data from core storage to the 20
secton of one disk track. Note: The Write Address
key must be on.
Compare addresses and data from the 20 secton of a
disk track with addresses and data in core storage.
stored in core storage in the location following the
read-in area provides the correct termination of the
operation.
A group mark can cause an incorrect termination,
which is indicated by the Wrong Length Record Check
indicator (37) being turned on. This occurs when there
is a group mark in core storage immediately following
the last character of any sector except the last sector
of the record.
Group marks in core storage positions other than
those immediately following a sector are simply re-
placed by data from disk storage; they do not affect
the operation.
Execution Time. Average T
==
22
+
25 ms