P89C51RB2HBA NXP Semiconductors, P89C51RB2HBA Datasheet - Page 16

• Manufacturer Part Number: P89C51RB2HBA
• Manufacturer: NXP Semiconductors

Specifications of P89C51RB2HBA

• Cpu Family: 89C
• Device Core: 80C51
• Device Core Size: 8b
• Frequency (max): 33MHz
• Interface Type: UART
• Program Memory Type: Flash
• Program Memory Size: 16KB
• Total Internal Ram Size: 512Byte
• # I/os (max): 32
• Number Of Timers - General Purpose: 3
• Operating Supply Voltage (typ): 5V
• Operating Supply Voltage (max): 5.5V
• Operating Supply Voltage (min): 4.5V
• Instruction Set Architecture: CISC
• Operating Temp Range: 0C to 70C
• Operating Temperature Classification: Commercial
• Mounting: Surface Mount
• Pin Count: 44
• Package Type: PLCC
• Lead Free Status / Rohs Status: Not Compliant

Philips Semiconductors
Table 3.
Baud Rate Generator Mode
Bits TCLK and/or RCLK in T2CON (Table 3) 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.
2002 May 24
12 clock
80C51 8-bit Flash microcontroller family
16KB/32KB/64KB ISP/IAP Flash with 512B/512B/1KB RAM
mode
375 k
9.6 k
2.8 k
2.4 k
1.2 k
300
110
300
110
OSC
T2EX Pin
Baud Rate
T2 Pin
Timer 2 Generated Commonly Used
Baud Rates
6 clock
mode
19.2 k
750 k
5.6 k
4.8 k
2.4 k
600
220
600
220
Transition
Detector
Osc Freq
C/T2 = 0
C/T2 = 1
12 MHz
12 MHz
12 MHz
12 MHz
12 MHz
12 MHz
12 MHz
6 MHz
6 MHz
Note availability of additional external interrupt.
EXEN2
RCAP2H
Control
Figure 6. 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
13
Timer 2
TL2
frequency in 12 clock mode). As a baud rate generator, it increments
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.
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
at the oscillator frequency in 6 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 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.
/
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 =
P89C51RB2/P89C51RC2/
[65536 + (RCAP2H, RCAP2L)]]
Oscillator Frequency
“1”
16 in 6 clock mode
32 in 12 clock mode
“1”
2
“0”
“0”
“0”
Overflow
Timer 1
P89C51RD2Hxx
“1”
OSC
1
/
12
/
16
2
16
16
the oscillator
in 12 clock mode).
SMOD
RCLK
TCLK
SU01213
Product data
RX Clock
TX Clock