Rainbow Electronics AT76C551 - Manual (Page 73)

73
AT76C551
1612D–08/01
Timer Prescale Register
R/W 16 bits
Timer Prescale Register sets the divisor for the prescale circuit. If Timer Prescale Register
contains p and PAI clock frequency is f (MHz) then countdown rate for the Timer Device
counter will be r = f/p
Note: The Timer Prescale Register must contain a non-zero value for proper Timer Device operation.
Timer Control Register
R/W 16 bits
• Bits 15..2 – Reserved
Returns 0 when read
• Bit 1 – Enable
Logic 1: The counter is allowed to run.
Logic 0: The counter is stopped. The Timer Device may be configured via Timer Preload Low
Register, Timer Preload High Register and Timer Prescale Register.
• Bit 0 – Periodic
Logic 1: Periodic mode operation is selected.
Logic 0: One-shot mode operation is selected.
Timer Interrupt Clear Register
W 16 bits
Writing Timer Interrupt Clear Register with any value clears an interrupt generated by the
Timer Device.
AT76C551 firmware is expected to write to Timer Interrupt Clear Register each time a Timer
Device interrupt is processed or else, interrupt request to the ARM core will persist.