Data Rate Select, Bits 0 - 1
These bits determine the data rate of the floppy controller. See Table 22 for the appropriate values.
No Precompensation, Bit 2
This bit can be set by software, but it has no functionality. It can be read by bit 2 of the DSR when in Model 30
register mode. Unaffected by software reset.
RESERVED, Bits 3 - 7
Bits 3 to 7 are RESERVED. Reserved bits cannot be written and return 0 when read.
Status Register Encoding
During the Result Phase of certain commands, the Data Register contains data bytes that give the status of the
command just executed.
.
Table 31 - Status Register 0
BIT
NO.
7,6
SYMBOL
IC
NAME
Interrupt
Code
DESCRIPTION
00 - Normal termination of command. The specified command was properly
executed and completed without error.
01 - Abnormal termination of command. Command execution was started,
but was not successfully completed.
10 - Invalid command. The requested command could not be executed.
11 - Abnormal termination caused by Polling.
5
4
SE
EC
Seek End
The FDC completed a Seek, Relative Seek or Recalibrate command (used
during a Sense Interrupt Command).
Equipment The TRK0 pin failed to become a “1” after:
Check
1. 80 step pulses in the Recalibrate command.
2. The Relative Seek command caused the FDC to step outward beyond
Track 0.
3
2
Unused. This bit is always “0”.
The current head address.
H
Head
Address
1,0
DS1,0
Drive
The current selected drive.
Select
Table 32 - Status Register 1
BIT
NO.
7
SYMBOL
EN
NAME
End of
Cylinder
DESCRIPTION
The FDC tried to access a sector beyond the final sector of the track (255D).
Will be set if TC is not issued after Read or Write Data command.
Unused. This bit is always “0”.
6
5
DE
OR
Data Error The FDC detected a CRC error in either the ID field or the data field of a
sector.
Overrun/
Underrun
4
Becomes set if the FDC does not receive CPU or DMA service within the
required time interval, resulting in data overrun or underrun.
Unused. This bit is always “0”.
3
2
ND
No Data
Any one of the following:
1. Read Data, Read Deleted Data command - the FDC did not find the
specified sector.
2. Read ID command - the FDC cannot read the ID field without an error.
3. Read A Track command - the FDC cannot find the proper sector
sequence.
1
NW
Not
Writable
WP pin became a “1” while the FDC is executing a Write Data, Write Deleted
Data, or Format A Track command.
SMSC DS – FDC37N769
Page 29 of 137
Rev. 02-16-07
DATASHEET
SMSC [ SMSC CORPORATION ]
