Jameco Electronics 3000, 2000 manual 1.Block Diagram of Timers A and B

11. TIMERS

There are two timers—Timer A and Timer B. Timer A is intended mainly for generating the clock for various peripherals, baud clock for the serial ports, a periodic clock for clocking Parallel Ports D and E, or for generating periodic interrupts. Timers A1–A7 are general-purpose timers, and Timers A8–A10 are dedicated to specific peripherals. Timer B can be used for the same functions, but it cannot generate the baud clock. Timer B is more flexible when it can be used because the program can read the time from a continu- ously running counter and events can be programmed to occur at a specified future time.

perclk	Timer A System
perclk				Serial E
A1
				A2
perclk/2				Serial F
				A3
				Serial A
				A4
			Input	Serial B
	A8			A5
			Capture
				Serial C
	A9		PWM	A6
				Serial D
			Quadrature
	A10			A7
			Decode
Timer A1
perclk/2	10-bit counter
perclk/8		10 bits		compare
				Timer_B1
Timer B System	match reg			Control Timer
				Synchronized
	match preload			outputs
				Timer_B2
	match reg
	match preload

Figure 11-1. Block Diagram of Timers A and B

User’s Manual 149