at89ls52-16si ATMEL Corporation, at89ls52-16si Datasheet - Page 17

• Manufacturer Part Number: at89ls52-16si
• Description: At89ls52, Low-voltage Microcontroller With 8k Bytes In-system Programmable Flash
• Manufacturer: ATMEL Corporation

Figure 11-1. Timer 2 in Clock-Out Mode
12. Programmable Clock Out
2601B–MICRO–03/05
(T2EX)
P1.0
P1.1
(T2)
A 50% duty cycle clock can be programmed to come out on P1.0, as shown in
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
4 MHz (for a 16 MHz 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.
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 gen-
erator 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.
OSC
TRANSITION
DETECTOR
÷2
Clock-Out Frequency
EXEN2
C/T2 BIT
EXF2
TR2
=
------------------------------------------------------------------------------------ -
4 x [65536-(RCAP2H,RCAP2L)]
÷2
Oscillator Frequency
TIMER 2
INTERRUPT
(8-BITS)
RCAP2L RCAP2H
TL2
T2OE (T2MOD.1)
(8-BITS)
TH2
AT89LS52
Figure
11-1. This
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