The control register (TACR) is laid out as shown in Table 11-4.

Table 11-4. Timer A Control Register

 

Timer A Control Register

(TACR)

(Address = 0x00A4)

 

 

 

 

 

Bit(s)

Value

 

Description

 

 

 

 

 

7

0

Timer A7 clocked by the main Timer A clock.

 

 

 

 

 

1

Timer A7 clocked by the output of Timer A1.

 

 

 

 

 

 

 

6

0

Timer A6 clocked by the main Timer A clock.

 

 

 

 

 

1

Timer A6 clocked by the output of Timer A1.

 

 

 

 

 

 

 

5

0

Timer A5 clocked by the main Timer A clock.

 

 

 

 

 

1

Timer A5 clocked by the output of Timer A1.

 

 

 

 

 

 

 

4

0

Timer A4 clocked by the main Timer A clock.

 

 

 

 

 

1

Timer A4 clocked by the output of Timer A1.

 

 

 

 

 

 

 

3

0

Timer A3 clocked by the main Timer A clock.

 

 

 

 

 

1

Timer A3 clocked by the output of Timer A1.

 

 

 

 

 

 

 

2

0

Timer A2 clocked by the main Timer A clock.

 

 

 

 

 

1

Timer A2 clocked by the output of Timer A1.

 

 

 

 

 

 

 

 

 

00

Timer A interrupts are disabled.

 

 

 

 

 

 

1:0

01

Timer A interrupts use Interrupt Priority 1.

 

 

 

 

 

10

Timer A interrupts use Interrupt Priority 2.

 

 

 

 

 

 

 

 

11

Timer A interrupts use Interrupt Priority 3.

 

 

 

 

 

 

The Timer A Prescale Register (TAPR) specifies the main clock for Timer A. This will affect all of the timer A countdown timers. By default Timer A is clocked by peripheral clock divided by two.

The prescale register (TAPR) is laid out as shown in Table 11-5.

Table 11-5. Timer A Prescale Register

 

Timer A Prescale Register

(TAPR)

(Address = 0x00A1)

 

 

 

 

 

 

Bit(s)

 

Value

 

Description

 

 

 

 

 

 

 

7:1

 

 

These bits are ignored.

 

 

 

 

 

 

 

0

 

0

The main clock for Timer A is the peripheral clock.

 

 

 

 

 

 

 

1

The main clock for Timer A is the peripheral clock divided by two.

 

 

 

 

 

 

 

 

154

Rabbit 3000 Microprocessor

Page 163
Image 163
Jameco Electronics 2000, 3000 manual Timer a Control Register, Timer a Prescale Register, Tacr, Tapr