Status Register O - IBM 5150 Hardware Reference Manual

Table 15.
Status Register
I
BIT
NO. NAME
SYMBOL
D7
End of Cylinder
EN
D6
-
­
D5
Data Error
DE
D4 Over Run
OR
D3
-
­
D2 No Data
ND
Dl Not Writable
NW
DO Missing Address
MA
Mark
DESCRIPTION
When the FD Ctries to access a sector
beyond the final sector of a cylinder,
this flag is set.
Not used. This bit is always 0 (low).
When the FDC detects a CRC error in
either the I D field or the data field,
~
this flag is set.
t;
~
If the FDC is not serviced by the main·
t;
systems during data transfers within a
f-
certain time interval, this flag is set.
Not used. This bit is always 0 (low).
During Execution of a Read Data, Write
Deleted Data, or Scan command, if the
FDC cannot find the sector specified
in the I D register, this flag is set.
During execution of the Read I D
command, if the FDC cannot read
the I D field without an error, then
this flag is set.
During the execution of the Read-a-
Cylinder command, if the starting
sector cannot be found, then this
flag is set.
During Execution of a Write Data, Write
Deleted Data, or Format aCyl inder
command, if the FDC detects a write
protect signal from the F DO, then this
flag is set.
If the FDC cannot detect the I D Address
Mark, this flag is set. Also at the same
time, the MD (Missing Address Mark in
Data Field) of Status Register 2 is set.
2-101