AP160

Version 0.0

11

AMIC Technology, Inc.

Programmable Clock Out

A 50% duty cycle clock can be programmed to come out on P1.0, as shown in Figure 5. This pin, besides being a regular

I/O pin, has two alternate functions. It can be programmed to input the external clock for Timer/Counter 2 or to output a 50%

duty cycle clock ranging from 61 HZ to 4MHZ at a 16MHZ operating frequency. To configure the Timer/Counter 2 as a clock

generator, bit C/T2 (T2CON.1) must be cleared and bit T2OE (T2MOD.1) must be set. Bit Tr2 (T2CON.2) starts and stops

the timer. The clock-out frequency depends on the oscillator frequency and the reload value of Timer 2 capture registers

(RCAP2H, RCAP2L), as shown in the following equation.

)]

2

,

2

(

65535

[

4

L

RCAP

H

RCAP

Frequency

Oscillator

Frequency

Out

Clock

−

×

=

−

In the clock-out mode, Timer 2 roll-overs will not generate an interrupt. This behavior is similar to when Timer 2 is used as a

baud-rate generator. It is possible to use Timer 2 as a baud-rate generator and a clock generator simultaneously. Note,

however, that the baud-rate and clock-out frequencies cannot be determined independently from one another since they

both use RCAP2H and RCAP2L.

TIMER 2

INTERRUPT

OSC

C/T2 BIT

TL2

(8 BITS)

TH2

(8 BITS)

RCAP2L

RCAP2H

EXF2

EXEN2

TR2

TRANSITION

DETECTOR

2

÷

2

÷

P1.0

(T2)

P1.1

(T2EX)

T2OE (T2MOD.1)

Figure 5. Timer 2 in Clock-Out Mode