
Preliminary W77C32
- 52 -
BAUD RATE GENERATOR MODE
The baud rate generator mode is enabled by setting either the RCLK or TCLK bits in T2CON register.
While in the baud rate generator mode, Timer/Counter 2 is a 16 bit counter with auto reload when the
count rolls over from FFFFh. However, rolling over does not set the TF2 bit. If EXEN2 bit is set, then
a negative transition of the T2EX pin will set EXF2 bit in the T2CON register and cause an interrupt
request.
C/T = T2CON.1
0
T2 = P1.0
T2CON.6
TR2 = T2CON.2
T2EX = P1.1
EXEN2 = T2CON.3
EXF2
Timer 2
overflow
Timer 2
Interrupt
TH2
TL2
RCAP2H
RCAP2L
1
Clock Source
Mode input
div. by 4 osc/2
div. by 64 osc/32
div. by 1024 osc/512
Figure 17. Baud Rate Generator Mode
Programmable Clock-out
Timer 2 is equipped with a new clock-out feature which outputs a 50% duty cycle clock on P1.0. It can
be invoked as a programmable clock generator. To configure Timer 2 with clock-out mode, software
must initiate it by setting bit T2OE = 1, C/T2 = 0 and CP/RL = 0. Setting bit TR2 will start the timer.
This mode is similar to the baud rate generator mode, it will not generate an interrupt while Timer 2
overflow. So it is possible to use Timer 2 as a baud rate generator and a clock generator at the same
time. The clock-out frequency is determined by the following equation:
The Clock-out Frequency = Oscillator Frequency / [4 X (RCAP2H,RCAP2L) ]
T2CON.6
TR2 = T2CON.2
T2EX = P1.1
EXEN2 = T2CON.3
EXF2
T2=P1.0
Timer 2
Interrupt
TH2
TL2
RCAP2H
RCAP2L
Clock Source
Mode input
div. by 4 osc/2
div. by 64 osc/32
div. by 1024 osc/512
1/2
Figure 18. Programmable Clock-Out Mode