Cirrus Logic EP73xx - Manual (Page 111)

EP7309/11/12 User’s Manual - DS508UM4 13-1
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Copyright Cirrus Logic, Inc. 2003
1313
13
Chapter 13
13 Dedicated LED Flasher
Introduction
LED flasher provides a user interface to toggle a specific GPIO pin for use to flash an
LED or other signaling device. A benefit of this feature is that the system, regardless
of the processor state, will continue to control this port. Only a system reset, loss of
power, or malfunction would prevent normal operation of the LED flasher.
LED Flasher Register List
Programming Example
;*****************************************************************************
; Program PD0/LEDFLSH for 50% duty on a 1 sec interval
;*****************************************************************************
LEDFLSH EQU 0x61
;
ldr r0, =0x80002000
mov r1, #LEDFLSH
str r1, [r0,#0x2C0]
;
Operational Overview
The LED flasher feature enables an external GPIO ( PD0 / LEDFLSH ) to be toggled at a
programmable rate and duty cycle with the intent of using this to toggle an LED. If
programmed,
PD0 will be dedicated to this task.
This module is driven from the RTC (32.768 kHz) oscillator and works in all running
modes because no CPU intervention is required.
The flash rate can be programmed from 1-4 seconds, and the duty cycle can vary from
1/15 to 15/16 with a 50% duty cycle at 8/16. The external pin can provide up to 4 ma
of drive current.
Table 13-1: LED Flasher Registers
Address Name Type Size Description Page
0x8000.22C0 LEDFLSH R/W 0 LED Flasher page 13-2