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P80C32EFBB View Datasheet(PDF) - Philips Electronics

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P80C32EFBB
Philips
Philips Electronics Philips
P80C32EFBB Datasheet PDF : 62 Pages
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Philips Semiconductors
CMOS single-chip 8-bit microcontrollers
Product specification
80C52/80C54/80C58
Timer 1
Overflow
OSC
NOTE: OSC. Freq. is divided by 2, not 12.
÷2
C/T2 = 0
T2 Pin
C/T2 = 1
Transition
Detector
Control
TR2
TL2
(8-bits)
TH2
(8-bits)
÷2
“0”
“1”
“1”
“0”
SMOD
RCLK
RCAP2L
Reload
RCAP2H
“1”
“0”
÷ 16
RX Clock
TCLK
÷ 16
TX Clock
T2EX Pin
EXF2
Timer 2
Interrupt
Control
EXEN2
Note availability of additional external interrupt.
Figure 6. Timer 2 in Baud Rate Generator Mode
SU00068
Table 3. Timer 2 Generated Commonly Used
Baud Rates
Baud Rate
Osc Freq
Timer 2
RCAP2H
RCAP2L
375K
12MHz
FF
FF
9.6K
12MHz
FF
D9
2.8K
12MHz
FF
B2
2.4K
12MHz
FF
64
1.2K
12MHz
FE
C8
300
12MHz
FB
1E
110
12MHz
F2
AF
300
6MHz
FD
8F
110
6MHz
F9
57
Baud Rate Generator Mode
Bits TCLK and/or RCLK in T2CON (Table 2) allow the serial port
transmit and receive baud rates to be derived from either Timer 1 or
Timer 2. When TCLK= 0, Timer 1 is used as the serial port transmit
baud rate generator. When TCLK= 1, Timer 2 is used as the serial
port transmit baud rate generator. RCLK has the same effect for the
serial port receive baud rate. With these two bits, the serial port can
have different receive and transmit baud rates – one generated by
Timer 1, the other by Timer 2.
Figure 6 shows the Timer 2 in baud rate generation mode. The baud
rate generation mode is like 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 given below:
Modes
1
and
3
Baud Rates
+ Timer
2
Overflow
16
Rate
The timer can be configured for either “timer” or “counter” operation.
In many applications, it is configured for “timer” operation (C/T2*=0).
Timer operation is different for Timer 2 when it is being used as a
baud rate generator.
Usually, as a timer it would increment every machine cycle (i.e., 1/12
the oscillator frequency). As a baud rate generator, it increments
every state time (i.e., 1/2 the oscillator frequency). Thus the baud
rate formula is as follows:
Modes 1 and 3 Baud Rates =
Oscillator Frequency
[32 [65536 * (RCAP2H, RCAP2L)]]
Where: (RCAP2H, RCAP2L)= The content of RCAP2H and
RCAP2L taken as a 16-bit unsigned integer.
The Timer 2 as a baud rate generator mode shown in Figure 6, is
valid only if RCLK and/or TCLK = 1 in T2CON register. Note that a
rollover in TH2 does not set TF2, and will not generate an interrupt.
Thus, the Timer 2 interrupt does not have to be disabled when
Timer 2 is in the baud rate generator mode. Also if the EXEN2
(T2 external enable flag) is set, a 1-to-0 transition in T2EX
(Timer/counter 2 trigger input) will set EXF2 (T2 external flag) but
will not cause a reload from (RCAP2H, RCAP2L) to (TH2,TL2).
Therefore when Timer 2 is in use as a baud rate generator, T2EX
can be used as an additional external interrupt, if needed.
1996 Aug 16
11
 

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