CS5530A datasheet(74/259 Pages) NSC

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Functional Description (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 GP Timer 1.

Primary floppy disk: I/O Port 3F2h, 3F4h, 3F5h, and 3F7

Secondary floppy disk: I/O Port 372h, 373h, 375h, and 377h

The active floppy 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 drive address range selected in F0 Index 93h[5] reloads GP Timer 1.

F0 Index 8Ah

General Purpose Timer 2 Count Register (R/W)

Reset Value = 00h

7:0

General Purpose Timer 2 Count: This register holds the load value for GP Timer 2. This value can represent either an 8-

bit or 16-bit timer (configured in F0 Index 8Bh[5]). It is loaded into the timer 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 timer is decremented with each clock of the configured timebase. Upon expiration of the timer, an SMI is generated and

the top level of status is F1BAR+Memory Offset 00h/02h[9] and the second level of status is reported in F1BAR+Memory

Offset 04h/06h[1]).

Once expired, this timer must be re-initialized by either disabling and enabling it, or writing a new count value here.

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

Index 90h[7]).

This timer’s timebase can be configured as 1 msec or 1 sec in F0 Index 8Bh[3].

F0 Index 8Bh

General Purpose Timer 2 Control Register (R/W)

Reset Value = 00h

Re-trigger General Purpose Timer 1 on Secondary Hard Disk Activity: 0 = Disable; 1 = Enable.

Any access to the secondary hard disk drive 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 ms; 1 = 32 µs.

General Purpose Timer 2 Shift: GP Timer 2 is treated as an 8-bit or 16-bit timer. 0 = 8-bit; 1 = 16-bit.

As an 8-bit timer, the count value is loaded into GP Timer 2 Count Register (F0 Index 8Ah).

As a 16-bit timer, 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 Shift: GP Timer 1 is treated as an 8-bit or 16-bit timer. 0 = 8-bit; 1 = 16-bit.

As an 8-bit timer, the count value is that loaded into GP Timer 1 Count Register (F0 Index 88h).

As a 16-bit timer, 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.

Timebase for General Purpose Timer 2: Selects timebase for GP Timer 2 (F0 Index 8Ah). 0 = 1 sec; 1 = 1 msec.

Re-trigger General Purpose Timer 2 on GPIO7 Pin Transition: A configured transition on the GPIO7 pin reloads GP

Timer 2 (F0 Index 8Ah). 0 = Disable; 1 = Enable.

F0 Index 92h[7] selects whether a rising- or a falling-edge transition acts as a reload. For GPIO7 to work here, it must first be

configured as an input (F0 Index 90h[7] = 0).

1:0

Reserved: Set to 0.

Table 3-28. General Purpose Timers and Control Registers (Continued)

Bit

Description

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