AP160 AMICC [AMIC Technology], AP160 Datasheet - Page 10

• Manufacturer Part Number: AP160
• Description: 8-BIT MICROCONTROLLER WITH 8KB OTP
• Manufacturer: AMICC [AMIC Technology]

Baud Rate Generator
Timer 2 is selected as the baud rate generator by setting TCLK and/or RCLK in T2CON (Table 2). Note that the baud rates
for transmit and receive can be different if Timer 2 is used for the receiver or transmitter and Timer 1 is used for the other
function. Setting RCLK and/or TCLK puts Timer 2 into its baud rate generator mode, as shown in Figure 4. The baud rate
generator mode is similar to the auto-reload mode, in that a rollover in Th2 causes the Timer 2 registers to be reloaded with
the 16-bit value in registers RCAP2H and RCAP2L, which are preset by software. The baud rates in modes 1 and 3 are
determined by Timer 2’s overflow rate according to the following equation.
The Timer can be configured for either timer or counter operation. In most applications, it is configured for timer operation
(CP/T2=0). The Timer operation is different for Timer 2 when it is used as a baud rate generator. Normally, as a timer, it
increments every machine cycle (at 1/12 the oscillator frequency). As a baud rate generator, however, it increments every
state time (at 1/2 the oscillator frequency). The baud rate formula is given below.
where (RCAP2H,RCAP2L) is the content of RCAP2H and RCAP2L taken as a 16-bit unsigned integer.
Timer 2 as a baud rate generator is shown in Figure 4. This figure is valid only if RCLK or TCLK=1 in T2CON. Note that a
rollover in TH2 does not ser TF2 and will not generate an interrupt. Note too, that if EXEN2 is set, a 1-to-0 transition in T2EX
will set EXF2 but will not cause a reload from (RCAP2H, RCAP2L) to (TH2,TL2). Thus when timer 2 is in use as a baud rate
generator, T2EX can be used as an extra external interrupt. Note that when Timer 2 is running (TR2=1) as a timer in the
baud rate generator mode. TH2 or TL2 should not be read from or written to. Under there conditions, the Timer is
incremented every state time, and the results of a read or write may not be accurate. The RCAP2 registers may be read but
should not be written to, because a write might overlap a reload and cause write and/or reload errors. The timer should be
turned off (clear TR2) before accessing the timer 2 or RCAP2 register.
Version 0.0
T2EX PIN
OSC
T2 PIN
2
TRANSITION
DETECTOR
Modes
NOTE:OSC FREQ. IS DIVIDED BY 2, NOT 12
Baud
Mode 1 and 3 Baud Rates =
C/T2=0
C/T2=1
Figure 4. Timer 2 in Baud Rate Generator Mode
1
Rate
and
3
EXEN2
TR2
32
CONTROL
CONTROL
[
65536
RCAP2H
Oscillator
TH2
10
Timer
EXF2
(
RCAP
RCAP2L
TL2
2
Frequency
Overflow
16
2
H
,
RCAP
INTERRUPT
TIMER 2
Rate
TIMER 1 OVERFLOW
"1"
"1"
2
2
L
"0"
)]
"0"
"0"
AMIC Technology, Inc.
"1"
16
16
RCLK
TCLK
AP160
SMOD1
CLOCK
CLOCK
RX
TX