SC2200 datasheet(219/433 Pages) NSC

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Core Logic Module (Continued)

Re-trigger General Purpose Timer 1 on Floppy Disk Activity.

0: Disable.

1: Enable.

Any access to the floppy disk drive address ranges listed below reloads General Purpose Timer 1:

— Primary floppy disk: I/O Port 3F2h-3F5h, 3F7h

— Secondary floppy disk: I/O Port 372h-375h, 377h

The active floppy disk drive is configured via F0 Index 93h[7].

Re-trigger General Purpose Timer 1 on Primary Hard Disk Activity.

0: Disable.

1: Enable.

Any access to the primary hard disk address range selected in F0 Index 93h[5], reloads General Purpose Timer 1.

Index 8Ah

General Purpose Timer 2 Count Register (R/W)

Reset Value: 00h

7:0

GPT2_COUNT. This field represents the load value for General Purpose Timer 2. This value can represent either an 8-bit or

16-bit counter (configured in F0 Index 8Bh[5]). It is loaded into the counter when the timer is enabled (F0 Index 83h[1] = 1).

Once the timer is enabled and a transition occurs on GPIO7, the timer is re-loaded.

The counter is decremented with each clock of the configured timebase (1 msec or 1 sec selected at F0 Index 8Bh[3]). Upon

expiration of the counter, an SMI is generated and the top level of status is F1BAR0+I/O Offset 00h/02h[9]. The second level

of status is reported at F1BAR0+I/O Offset 04h/06h[1]). Once expired, this counter must be re-initialized by either disabling

and enabling it, or by writing a new count value in this register.

For GPIO7 to act as the reload for this counter, it must be enabled as such (F0 Index 8Bh[2]) and be configured as an input.

(GPIO pin programming is at F0BAR0+I/O Offset 20h and 24h.)

Index 8Bh

General Purpose Timer 2 Control Register (R/W)

Reset Value: 00h

Re-trigger General Purpose Timer 1 (GP Timer 1) on Secondary Hard Disk Activity.

0: Disable.

1: Enable.

Any access to the secondary hard disk address range selected in F0 Index 93h[4] reloads GP Timer 1.

VGA Timer Base. Selects timebase for VGA Timer Register (F0 Index 8Eh).

0: 1 millisecond.

1: 32 microseconds.

General Purpose Timer 2 (GP Timer 2) Shift. GP Timer 2 is treated as an 8-bit or 16-bit timer.

0: 8-bit. The count value is loaded into GP Timer 2 Count Register (F0 Index 8Ah).

1: 16-bit. The value loaded into GP Timer 2 Count Register is shifted left by eight bits, the lower eight bits become zero,

and this 16-bit value is used as the count for GP Timer 2.

General Purpose Timer 1 (GP Timer 1) Shift. GP Timer 1 is treated as an 8-bit or 16-bit timer.

0: 8-bit. The count value is that loaded into GP Timer 1 Count Register (F0 Index 88h).

1: 16-bit. The value loaded into GP Timer 1 Count Register is shifted left by eight bit, the lower eight bits become zero, and

this 16-bit value is used as the count for GP Timer 1.

General Purpose Timer 2 (GP Timer 2) Timebase. Selects timebase for GP Timer 2 (F0 Index 8Ah).

0: 1 second.

1: 1 millisecond.

Re-trigger Timer on GPIO7 Pin Transition. A rising-edge transition on the GPIO7 pin reloads GP Timer 2 (F0 Index 8Ah).

0: Disable.

1: Enable.

For GPIO7 to work here, it must first be configured as an input. (GPIO pin programming is at F0BAR0+I/O Offset 20h and

24h.)

1:0

Reserved. Set to 0.

Table 5-29. F0: PCI Header and Bridge Configuration Registers for GPIO and LPC Support (Continued)

Bit

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SC2200 Datasheet(PDF) 219 Page - National Semiconductor (TI)

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