CL-PS7500FE 查看數據表（PDF） - Cirrus Logic

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CL-PS7500FE

System-on-a Chip for Internet Appliance

Cirrus Logic 

CL-PS7500FE

System-on-a-Chip for Internet Appliance

11.11.1 Programming the Timers

The locations of the registers can be found in Chapter 10.

A write to the following registers updates the values as described below:

T0low

updates the value in the lower half of the timer 0 input latch

T0high

updates the value in the upper half of the timer 0 input latch with the

written value.

T0GO

loads the counters immediately with the value programmed into the

input latch. If the counter is loaded with ‘0’ it is continuously reload.

T0LAT

places the current count value in the output latch.

A read of the following registers updates the values as described below:

T0high

returns the upper 8 bits of the count value

T0low

returns the lower 8 bits of the count value.

11.11.2 Timer interrupts

Each timer generates an interrupt when it reaches zero and is reloaded. These interrupts are handled by

the IRQA set of interrupt processing registers (bits 5 and 6).

The timers can be used to generate timed interrupts at regular intervals, T, where:

T = (T0low + (256 × T0high)) × 0.5 µs

Equation 11-1

11.12 General-Purpose, 8-Bit-Wide I/O Port

A general-purpose 8-bit-wide I/O port is included in the CL-PS7500FE. The eight open drain output pins

IOP[7:0] can be driven low or monitored as inputs by using the IOLINES register at address 0x0320000C.

When read, this register returns the current value seen at the IOP[7:0] pins. When written to, each bit con-

trols the status of the corresponding IOP pin. When a one is written to a bit, that pin's output enable is

switched off and it can be driven as an input. When a ‘0’ is written to a bit, the corresponding output pin

is forced low.

There is a complete set of three interrupt control and status registers (IRQD) for the IOP pins that allow

any bit to generate a unique interrupt. The interrupt is generated when the corresponding IOP bit is low.

120

I/O SUBSYSTEMS

ADVANCE DATA BOOK v2.0

June 1997

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