BIT 6 DMA REQUEST
Active high status of the DMA request pending.
BIT 7 INTERRUPT PENDING
Active high bit indicating the state of the Floppy Disk Interrupt.
STATUS REGISTER B (SRB)
Address 3F1 READ ONLY
This register is read-only and monitors the state of several disk interface pins in PS/2 and Model 30 modes. The SRB
can be accessed at any time when in PS/2 mode. In the PC/AT mode the data bus pins D0 - D7 are held in a high
impedance state for a read of address 3F1.
PS/2 Mode
7
1
6
1
5
4
3
2
1
0
MOT
EN0
0
DRIVE WDATA RDATA WGATE MOT
SEL0 TOGGLE TOGGLE
EN1
0
RESET
COND.
1
1
0
0
0
0
BIT 0 MOTOR ENABLE 0
Active high status of the MTR0 disk interface output pin. This bit is low after a hardware reset and unaffected by a
software reset.
BIT 1 MOTOR ENABLE 1
Active high status of the MTR1 disk interface output pin. This bit is low after a hardware reset and unaffected by a
software reset.
BIT 2 WRITE GATE
Active high status of the WGATE disk interface output.
BIT 3 READ DATA TOGGLE
Every inactive edge of the RDATA input causes this bit to change state.
BIT 4 WRITE DATA TOGGLE
Every inactive edge of the WDATA input causes this bit to change state.
BIT 5 DRIVE SELECT 0
Reflects the status of the Drive Select 0 bit of the DOR (address 3F2 bit 0). This bit is cleared after a hardware reset
and it is unaffected by a software reset.
BIT 6 RESERVED
Always read as a logic "1".
BIT 7 RESERVED
Always read as a logic "1".
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