P83C654X2FBD/CV710 NXP Semiconductors, P83C654X2FBD/CV710 Datasheet - Page 19

• Manufacturer Part Number: P83C654X2FBD/CV710
• Description: 8-bit Microcontrollers - MCU P83C654X2FBD/LQFP44/TRAYBM//CV
• Manufacturer: NXP Semiconductors

Specifications of P83C654X2FBD/CV710

• Core: 80C51
• Data Bus Width: 8 bit
• Maximum Clock Frequency: 16 MHz
• Program Memory Size: 16 KB
• Data Ram Size: 256 B
• Operating Supply Voltage: 5 V
• Package / Case: SOT-187-2
• Mounting Style: SMD/SMT
• Interface Type: I2C, Serial
• Number Of Programmable I/os: 4
• Number Of Timers: 3
• Processor Series: 80C51
• Program Memory Type: OTP EPROM

Philips Semiconductors
Table 4.
Baud Rate Generator Mode
Bits TCLK and/or RCLK in T2CON (Table 4) 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 12 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.
2004 Apr 20
12-clock
80C51 8-bit microcontroller family
256B RAM, low voltage (2.7 to 5.5 V), low power, high speed
(30/33 MHz)
mode
375 k
OSC
9.6 k
4.8 k
2.4 k
1.2 k
300
110
300
110
T2EX Pin
n = 1 in 6-clock mode
n = 2 in 12-clock mode
Baud Rate
T2 Pin
Timer 2 Generated Commonly Used
Baud Rates
6-clock
n
mode
19.2 k
750 k
9.6 k
4.8 k
2.4 k
600
220
600
220
Transition
Detector
Osc Freq
12 MHz
12 MHz
12 MHz
12 MHz
12 MHz
12 MHz
12 MHz
6 MHz
6 MHz
C/T2 = 0
C/T2 = 1
Note availability of additional external interrupt.
EXEN2
RCAP2H
16 kB OTP/ROM,
Control
Figure 12. Timer 2 in Baud Rate Generator Mode
FF
FF
FF
FF
FE
FB
FD
F2
F9
TR2
Timer 2
Control
RCAP2L
EXF2
D9
C8
AF
FF
B2
64
1E
8F
57
RCAP2L
(8-bits)
Interrupt
19
Timer 2
TL2
In many applications, it is configured for “timer” operation (C/T2 = 0).
The baud rates in modes 1 and 3 are determined by Timer 2’s
overflow rate given below:
The timer can be configured for either “timer” or “counter” operation.
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
frequency in 12-clock mode). As a baud rate generator, it
increments at the oscillator frequency in 6-clock mode (
12-clock mode). Thus the baud rate formula is as follows:
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 12, 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.
/
6
the oscillator frequency in 6-clock mode,
Modes 1 and 3 Baud Rates + Timer 2 Overflow Rate
Modes 1 and 3 Baud Rates =
(8-bits)
RCAP2H
TH2
Reload
[ n *
* n =
P83C654X2/P87C654X2
[65536 * (RCAP2H, RCAP2L)]]
Oscillator Frequency
“1”
16 in 6-clock mode
32 in 12-clock mode
“1”
2
“0”
“0”
“0”
Overflow
Timer 1
“1”
1
/
12
16
16
16
the oscillator
SMOD
RCLK
TCLK
SU01629
OSC
Product data
RX Clock
TX Clock
/
2
in