
SMSC DS – LPC47M192
Page 61
Rev. 03/30/05
DATASHEET
Configure
The Configure command is issued to select the special features of the FDC. A Configure command need not be
issued if the default values of the FDC meet the system requirements.
Table 26 – Drive Control Delays (ms)
HUT
SRT
2M
64
4
..
56
60
1M
128
8
..
112
120
500K
256
16
..
224
240
300K
426
26.7
..
373
400
250K
512
32
..
448
480
2M
4
3.75
..
0.5
0.25
1M
8
7.5
..
1
0.5
500K
16
15
..
2
1
300K
26.7
25
..
3.33
1.67
250K
32
30
..
4
2
0
1
..
E
F
HLT
2M
64
0.5
1
..
63
63.5
1M
128
1
2
..
126
127
500K
256
2
4
..
252
254
300K
426
3.3
6.7
..
420
423
250K
512
4
8
.
504
508
00
01
02
..
7F
7F
Configure Default Values:
EIS - No Implied Seeks
EFIFO - FIFO Disabled
POLL - Polling Enabled
FIFOTHR - FIFO Threshold Set to 1 Byte
PRETRK - Pre-Compensation Set to Track 0
EIS - Enable Implied Seek. When set to "1", the FDC will perform a Seek operation before executing a read or write
command. Defaults to no implied seek.
EFIFO - A "1" disables the FIFO (default). This means data transfers are asked for on a byte-by-byte basis. Defaults to
"1", FIFO disabled. The threshold defaults to "1".
POLL - Disable polling of the drives. Defaults to "0", polling enabled. When enabled, a single interrupt is generated
after a reset. No polling is performed while the drive head is loaded and the head unload delay has not expired.
FIFOTHR - The FIFO threshold in the execution phase of read or write commands. This is programmable from 1 to 16
bytes. Defaults to one byte. A "00" selects one byte; "0F" selects 16 bytes.
PRETRK - Pre-Compensation Start Track Number. Programmable from track 0 to 255. Defaults to track 0. A "00"
selects track 0; "FF" selects track 255.
Version
The Version command checks to see if the controller is an enhanced type or the older type (765A). A value of 90 H is
returned as the result byte.
Relative Seek
The command is coded the same as for Seek, except for the MSB of the first byte and the DIR bit.
DIR
Head Step Direction Control
RCN
Relative Cylinder Number that determines how many tracks to step the head in or out from
the current track number.