W83977G Winbond Electronics Corp America, W83977G Datasheet - Page 41

• Manufacturer Part Number: W83977G
• Description: W83877TF plus KBC, CIR, RTC, Pb-free
• Manufacturer: Winbond Electronics Corp America

5.2.5
The Main Status Register is used to control the flow of data between the microprocessor and the
controller. The bit definitions for this register are as follows:
5.2.6
The Data Rate Register is used to set the transfer rate and write precompensation. The data rate of
the FDC is programmed by the CC REGISTER for PC-AT and PS/2 Model 30 and PS/2 mode, and
not by the DR REGISTER. The real data rate is determined by the most recent write to either of the
DR REGISTER or CC REGISTER.
S/W RESET (Bit 7):
This bit is the software reset bit.
POWER-DOWN (Bit 6):
0
1
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.
7
W83977F-A/ W83977G-A/ W83977AF-A/ W83977AG-A
FDC in normal mode
FDC in power-down mode
6
5
Main Status Register (MS Register) (Read base address + 4)
Data Rate Register (DR Register) (Write base address + 4)
4
3
2
1
7
0
FDD 2 Busy, (D2B = 1), FDD number 2 is in the SEEK mode.
FDD 0 Busy, (D0B = 1), FDD number 0 is in the SEEK mode.
FDD 1 Busy, (D1B = 1), FDD number 1 is in the SEEK mode.
FDD 3 Busy, (D3B = 1), FDD number 3 is in the SEEK mode.
FDC Busy, (CB). A read or write command is in the process when CB = HIGH.
Non-DMA mode, the FDC is in the non-DMA mode, this bit is set only during the
execution phase in non-DMA mode.
Transition to LOW state indicates execution phase has ended.
DATA INPUT/OUTPUT, (DIO). If DIO= HIGH then transfer is from Data Register to the processor.
Request for Master (RQM). A high on this bit indicates Data Register is ready to send or receive data to or from the processor.
If DIO = LOW then transfer is from processor to Data Register.
6
5
0
4
3
-33 -
2
1
0
DRATE0
DRATE1
PRECOMP0
PRECOMP1
PRECOMP2
POWER DOWN
S/W RESET
Publication Release Date: May 2006
Revision 0.60