W83877TF Datasheet, PDF (105/154 Pages) Winbond – I/O chip disk drive adapter

W83877TF
EN3MODE (Bit 5):
This bit enables or disables three mode FDD selection. When this bit is high, it enables the read/write
3F3H register.
0
Disables 3 mode FDD selection
1
Enables 3 mode FDD selection
When three mode FDD function is enabled, the value of RWC depends on bit 5 and bit 4 of
TDR(3F3H). The values of RWC and their meaning are shown in Table 8-4.
Table 8-4
BIT 5 OF TDR
0
0
1
1
BIT 4 OF TDR
0
1
0
1
RWC
Normal
0
1
X
RWC = 0
250K bps
1.2 M FDD
X
X
RWC = 1
500K bps
X
1.4M FDD
X
Bit 4: Reserved.
CHIP ID 3, CHIP ID 2, CHIP ID 1, CHIP ID 0 (Bit 3-bit 0):
These four bits are read-only bits that contain chip identification information. The value is 0CH for
W83877TF during a read.
8.2.11 Configuration Register A (CR0A), default = 00H
When the device is in Extended Function mode and EFIR is 0AH, the CRA register can be accessed
through EFDR. This register is reserved.
8.2.12 Configuration Register B (CR0B), default = 0CH
When the device is in Extended Function mode and EFIR is 0BH, the CRB register can be accessed
through EFDR. The bit definitions are as follows:
765 43 ²¹ 0
DRV2EN
INVERTZ
MFM
IDENT
ENIFCHG
RXW4C
TXW4C
reserved
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Publication Release Date: March 1998
Version 0.61