
82801AA and 82801AB Datasheet
9-9
IDE Controller Registers (D31:F1)
9.1.17
SDMA_TIM—Synchronous DMA Timing Register
(IDE—D31:F1)
Address Offset:
Default Value:
4A
–
4Bh
0000h
Attribute:
Size:
R/W
16 bits
Bit
Description
15:14
Reserved.
13:12
Secondary Drive 1 Cycle Time (SCT1).
For Sync DMA mode. The setting of these bits determines
the minimum write strobe cycle time (CT). The DMARDY#-to-STOP (RP) time is also determined by
the setting of these bits.
11:10
Reserved.
9:8
Secondary Drive 0 Cycle Time (SCT0).
For Sync DMA mode. The setting of these bits determines
the minimum write strobe cycle time (CT). The DMARDY#-to-STOP (RP) time is also determined by
the setting of these bits.
7:6
Reserved.
5:4
Primary Drive 1 Cycle Time (PCT1).
For Sync DMA mode, the setting of these bits determines the
minimum write strobe cycle time(CT). The DMARDY#-to-STOP (RP) time is also determined by the
setting of these bits.
3:2
Reserved.
1:0
Primary Drive 0 Cycle Time (PCT0).
For Sync DMA mode, the setting of these bits determines the
minimum write strobe cycle time (CT). The DMARDY#-to-STOP (RP) time is also determined by the
setting of these bits.
SCB1 = 0 (33 MHz clock)
00 = CT 4 clocks, RP 6 clocks
01 = CT 3 clocks, RP 5 clocks
10 = CT 2 clocks, RP 4 clocks
11 = Reserved
SCB1 = 1 (66 MHz clock) (ICH 82801AA only)
00 = Reserved
01 = CT 3 clocks, RP 8 clocks
10 = CT 2 clocks, RP 8 clocks
11 = Reserved
SCB0 = 0 (33 MHz clock)
00 = CT 4 clocks, RP 6 clocks
01 = CT 3 clocks, RP 5 clocks
10 = CT 2 clocks, RP 4 clocks
11 = Reserved
SCB0 = 1 (66 MHz clock) (ICH 82801AA only)
00 = Reserved
01 = CT 3 clocks, RP 8 clocks
10 = CT 2 clocks, RP 8 clocks
11 = Reserved
PCB1 = 0 (33 MHz clock)
00 = CT 4 clocks, RP 6 clocks
01 = CT 3 clocks, RP 5 clocks
10 = CT 2 clocks, RP 4 clocks
11 = Reserved
PCB1 = 1 (66 MHz clock) (ICH 82801AA only)
00 = Reserved
01 = CT 3 clocks, RP 8 clocks
10 = CT 2 clocks, RP 8 clocks
11 = Reserved
PCB0 = 0 (33 MHz clock)
00 = CT 4 clocks, RP 6 clocks
01 = CT 3 clocks, RP 5 clocks
10 = CT 2 clocks, RP 4 clocks
11 = Reserved
PCB0 = 1 (66 MHz clock) (ICH 82801AA only)
00 = Reserved
01 = CT 3 clocks, RP 8 clocks
10 = CT 2 clocks, RP 8 clocks
11 = Reserved