Timer

4.1Introduction

Two timers are defined as the minimum provided within a system, although this may easily be expanded. The same principle of simple expansion has been applied to the register configuration which allows more complex timers to be used which are, from the programmer's model, compatible with those defined.

Each timer is a 16 bit wide down counter with selectable pre-scale. The pre-scaler allows either the system clock to be used directly, or the clock divided by 16 or 256 may be used. This is provided by 0, 4 or 8 stages of pre-scale.

Two modes of operation are available, free-running and periodic timer. In periodic timer mode the counter will generate an interrupt at a constant interval. In free-running mode the timer will overflow after reaching its zero value and continue to count down from the maximum value.

4-2	Reference Peripherals Specification
	ARM DDI 0062D

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