ACT apricot - Page 122

FLOPPY DISK INTERFACE
FDC to write the computed two-byte CRC character onto
the disk.
Failure of
the lOP to write the first byte to the Data
Register before the arrival of the leading edge of the Index
Pulse causes the FDC to, set the Lost Data bit in the Status
Register, activate the INTRQ output, and abort the
command. Failure of the lOP to supply a data byte to the
Data Register on receiving a DMA request after the first
byte, causes
the FDC to write a byte of zeroes onto the disk
and also set the Lost Data bit, but does not terminate the J
command sequence.
Status Register. The format of the Status Register following
a
formatting command is as detailed below. On issuing a
command to the Command Register, the FDC resets the
Status Register to monitor certain status conditions implied
by the new command. Due to internal timing delays, the
Status Register does not contain valid status information,
until 14 /LS after the new command is issued.
I s71 s61 s51 s41 s31 s21 Sl I so I Status Register
I L Busy
~DRQ
~
Lost Data
CRC Error
RNF
Logic 0
Protected
'------ Not Ready