PC97338VLJ datasheet(47/221 Pages) NSC

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latch (e.g., 74LS175). Address 3F2h is used if the

FDC is located at the primary address (bit 5 of

FER = 0) and address 372h is used if the FDC is

located at the secondary address (bit 5 of FER =

1).

2.3.3

Function Address Register (FAR),

Index 01h

In Plug and Play mode, this register is ignored.

In Legacy mode, this register selects the ISA I/O ad-

dress range to which each peripheral function re-

sponds.

FIGURE 4. FAR Register Bitmap

Bits 1,0 - Parallel Port Address

These bits select the parallel port address as

shown in Table 11.

TABLE 11. Parallel Port Addresses

Bits 3,2 - SCC1 Address

These bits determine which ISA I/O address range

is associated with SCC1 as shown in Table 13.

TABLE 12. COM Port Selection for SCC1

Bits 5,4 - SCC2 Address

These bits determine which ISA I/O address range

is associated with SCC2 as shown in Table 12.

TABLE 13. COM Port Selection for SCC2

Bits 7,6 - Select COM3 or COM4

These bits select the addresses that are used for

COM3 and COM4 as shown in Table 14.

TABLE 14. Address Selection for COM3 and

COM4

2.3.4

Power and Test Register (PTR),

Index 02h

This register determines the power-down method

used and whether hardware power-down is enabled,

and provides a bit for software power down of all en-

abled functions. It selects whether IRQ7 or IRQ5 is

associated with LPT2. It puts the enabled SCCs into

their test mode. Independent of this register the floppy

disk controller can enter low power mode via the

MODE command or the Data Rate Select (DSR) reg-

ister.

FAR

Parallel Port

Address

Interrupt

Bit 1 Bit 0

LPT2

(378-37F)

IRQ5 a

a. The interrupt assigned to this address can be

changed to IRQ7 by setting bit 3 of the Power

and Test Register (PTR)

LPT1

(3BC-3BE)

IRQ7

LPT3

(278-27F)

IRQ5

Reserved

TRI-STATE

(CTR4=0)

543

Reset

Required

Function Address

Index 01h

Parallel Port Address

SCC1 Address

SCC2 Address

Select COM3 or COM4

FAR

SCC1

Bit 3

Bit 2

COM Port #

0(default)

0(default) COM1

(3F8-F)

COM2

(2F8-F)

COM3

(See Table 14.)

COM4

(See Table 14.)

FAR

SCC2

Bit 5

Bit 4

COM#

COM1

(3F8-F)

0(default) 1(default) COM2

(2F8-F)

COM3

(See Table 14.)

COM4

(See Table 14.)

Bit 7

Bit 6

COM3 IRQ4

COM4 IRQ3

3E8-Fh

2E8-Fh

338-Fh

238-Fh

2E8-Fh

2E0-7h

220-7h

228-Fh

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