SC2200 NSC [National Semiconductor], SC2200 Datasheet - Page 224

• Manufacturer Part Number: SC2200
• Description: Thin Client On a Chip
• Manufacturer: NSC [National Semiconductor]

www.national.com
Core Logic Module
Table 5-29. F0: PCI Header and Bridge Configuration Registers for GPIO and LPC Support (Continued)
Index B6h
Index B7h
Index B8h
Index B9h
7:0
7:0
7:0
7:0
Bit
Description
Floppy Port 372h Shadow. Last written value of I/O Port 372h. Required for support of FDC power On/Off and 0V Sus-
pend/Resume coherency.
This register is a copy of an I/O register which cannot safely be directly read. The value in this register is not deterministic of
when the register is being read. It is provided here to assist in a Suspend-to-Disk operation.
Floppy Port 377h Shadow. Last written value of I/O Port 377h. Required for support of FDC power On/Off and 0V Sus-
pend/Resume coherency.
This register is a copy of an I/O register which cannot safely be directly read. The value in this register is not deterministic of
when the register is being read. It is provided here to assist in a Suspend-to-Disk operation.
DMA Shadow. This 8-bit port sequences through the following list of shadowed DMA Controller registers. At power on, a
pointer starts at the first register in the list and continuing through the other registers in subsequent reads according to the
read sequence. A write to this register resets the read sequence to the first register. Each shadow register in the sequence
contains the last data written to that location.
The read sequence for this register is:
1. DMA Channel 0 Mode Register
2. DMA Channel 1 Mode Register
3. DMA Channel 2 Mode Register
4. DMA Channel 3 Mode Register
5. DMA Channel 4 Mode Register
6. DMA Channel 5 Mode Register
7. DMA Channel 6 Mode Register
8. DMA Channel 7 Mode Register
9. DMA Channel Mask Register (bit 0 is channel 0 mask, etc.)
10. DMA Busy Register (bit 0 or 1 means a DMA occurred within last 1 msec, all other bits are 0)
PIC Shadow. This 8-bit port sequences through the following list of shadowed Interrupt Controller registers. At power on, a
pointer starts at the first register in the list and continuing through the other registers in subsequent reads according to the
read sequence. A write to this register resets the read sequence to the first register. Each shadow register in the sequence
contains the last data written to that location.
The read sequence for this register is:
1. PIC1 ICW1
2. PIC1 ICW2
3. PIC1 ICW3
4. PIC1 ICW4 - Bits [7:5] of ICW4 are always 0.
5. PIC1 OCW2 - Bits [6:3] of OCW2 are always 0 (See Note).
6. PIC1 OCW3 - Bits [7:4] are 0 and bits [6:3] are 1.
7. PIC2 ICW1
8. PIC2 ICW2
9. PIC2 ICW3
10. PIC2 ICW4 - Bits [7:5] of ICW4 are always 0.
11. PIC2 OCW2 - Bits [6:3] of OCW2 are always 0 (See Note).
12. PIC2 OCW3 - Bits [7:4] are 0 and bits [6:3] are 1.
Note:
To restore OCW2 to the shadow register value, write the appropriate address twice. First with the shadow register
value, then with the shadow register value ORed with C0h.
(Continued)
Floppy Port 372h Shadow Register (RO)
Floppy Port 377h Shadow Register (RO)
DMA Shadow Register (RO)
PIC Shadow Register (RO)
224
Reset Value: xxh
Reset Value: xxh
Reset Value: xxh
Reset Value: xxh
Revision 3.0