W83877TF/W83877TG
-32 -
S/W RESET (Bit 7):
This bit is the software reset bit.
POWER-DOWN (Bit 6):
0 FDC in normal mode
1 FDC in power-down mode
PRECOMP2 PRECOMP1 PRECOMP0 (Bit 4, 3, 2):
These three bits select the value of write precompensation. The following tables show the
precompensation values for the combination of these bits.
PRECOM
PRECOMPENSATION DELAY
2 1 0
250K - 1Mbps 2 Mbps Tape drive
0 0 0 Default Delays Default Delays
0 0 1 41.67 nS 20.8nS
0 1 0 83.34 nS 41.17nS
0 1 1 125.00 nS 62.5nS
1 0 0 166.67 nS 83.3nS
1 0 1 208.33 nS 104.2nS
1 1 0 250.00 nS 125.00nS
1 1 1 0.00 nS (disabled) 0.00nS (disabled)
DATA RATE DEFAULT PRECOMPENSATION DELAYS
250 KB/S 125 nS
300 KB/S 125 nS
500 KB/S 125 nS
1 MB/S 41.67 nS
2 MB/S 20.8 nS
DRATE1 DRATE0 (Bit 1, 0):
These two bits select the data rate of the FDC and reduced write current control.
00 500 KB/S (MFM), 250 KB/S (FM), RWC = 1.
01 300 KB/S (MFM), 150 KB/S (FM),
RWC = 0.
10 250 KB/S (MFM), 125 KB/S (FM),
RWC = 0.
11 1 MB/S (MFM), Illegal (FM),
RWC = 1.
The 2MB/S data rate for Tape drive is only supported by setting 01 to DRATE1 and DRATE0 bits, as
well as setting 10 to DRTA1 and DRTA0 bits which are two of the Configuration CR2D. Please refer to
the function of CR2D and the data rate table for individual data rates setting.
