Jameco Electronics Rabbit 3000 - Manual (Page 158)

User’s Manual 149
11. T
IMERS
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.
Figure 11-1. Block Diagram of Timers A and B
A1
A2
Timer A System
match reg
match reg
compare
Timer B System
match preload
match preload
10 bits Timer_B1
Timer_B2
A3
A4
A5
A6
A7
perclk
perclk
perclk/2
10-bit counter
A8
Serial E
Serial F
Serial A
Serial B
Serial C
Serial D
Input
Capture
PWM
Quadrature
Decode
A9
A10
Timer A1
perclk/2
perclk/8
Control Timer
Synchronized
outputs