PC87338 datasheet(56/221 Pages) NSC

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2.3.18 SuperI/O Chip Configuration

Upon reset, SCF1 is initialized to xx00000x.

FIGURE 19. SCF1 Register Bitmap

Bit 0 - Reserved

This bit is reserved.

Bits 2,1 - ECP DMA Number

Reported ECP DMA number, as reflected on bits

1,0 of the CNFGB ECP register. Bit 2 of SCF1 is

reflected on bit 1 of CNFGB and bit 1 of SCF1 on

bit 0 of CNFGB.

Microsoft’s ECP Protocol and ISA Interface Stan-

dard defines these bits as shown in Table 18.

TABLE 18. ECP DMA Option Selection

Bits 5-3 - Parallel Port DMA Plug and Play Support

Upon reset these bits are initialized to 000.

When a DMA request signal, i.e., DRQ0, DRQ1,

DRQ2 or DRQ3, is not configured as an FDC DMA

request signal, a parallel port DMA request signal

or a SCC2 DMA request signal, it is in TRI-STATE.

When a DMA acknowledge signal, i.e., DACK0,

DACK1, DACK2 or DACK3, is not configured as

an FDC DMA acknowledge signal, a parallel port

DMA acknowledge signal or a SCC2 DMA ac-

knowledge signal, it is ignored.

TABLE 19. Parallel Port Plug and Play DMA Set-

tings

Bits 7-6 - Reserved

These bits are reserved.

Bit 2

Bit 1

Selected DMA Option

Jumpered 8-bit DMA (Default)

DMA Channel 1 selected

DMA Channel 2 selected

DMA Channel 3 selected

Reserved

ECP DMA Number

Parallel Port DMA

Plug and Play Support

543

Reset

Required

Index 18h

SuperI/O Chip

Configuration

Bit 5 Bit 4 Bit 3

Parallel Port DMA

Plug and Play Setting

Disabled. Parallel port’s DMA is

not connected to any ISA DMA

channel, i.e., it is not connected to

any of the chip’s DMA pins.

It is the software’s responsibility to

route all DMA sources onto the

ISA DMA channels correctly.

Parallel port‘s DMA request and

acknowledge signals are

connected to DRQ0 and DACK0

pins.

Parallel port‘s DMA request and

acknowledge signals are

connected to DRQ1 and DACK1

pins.

Parallel port‘s DMA request and

acknowledge signals are

connected to DRQ2 and DACK2

pins.

Parallel port‘s DMA request and

acknowledge signals are

connected to DRQ3 and DACK3

pins.

101

Reserved

110

Reserved

111

Reserved

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