LPC47N227TQFP Standard Microsystems (SMSC), LPC47N227TQFP Datasheet - Page 63

• Manufacturer Part Number: LPC47N227TQFP
• Manufacturer: Standard Microsystems (SMSC)

Specifications of LPC47N227TQFP

• Lead Free Status / RoHS Status: Not Compliant

remaining step pulses. The HLT (Head Load Time) defines the time between when the Head Load
signal goes high and the read/write operation starts. The values change with the data rate speed
selection and are documented in Table 26. The values are the same for MFM and FM.
The choice of DMA or non-DMA operations is made by the ND bit. When this bit is "1", the non-DMA
mode is selected, and when ND is "0", the DMA mode is selected. In DMA mode, data transfers are
signaled by the DMA request cycles. Non-DMA mode uses the RQM bit and the interrupt to signal data
transfers.
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.
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.
7F
7F
00
01
02
E
0
1
..
F
..
2M
64
56
60
4
..
63.5
2M
0.5
64
63
1
..
128
112
120
1M
8
..
500K
Table 26 – Drive Control Delays (ms)
256
224
240
16
..
HUT
128
126
127
1M
1
2
..
300K
26.7
426
373
400
..
250K
512
448
480
32
..
63
500K
256
252
254
2
4
..
3.75
0.25
2M
0.5
4
..
HLT
1M
7.5
0.5
8
..
1
300K
426
420
423
3.3
6.7
..
500K
16
15
..
2
1
SRT
300K
26.7
3.33
1.67
25
..
250K
512
504
508
4
8
.
250K
32
30
..
4
2