p89cv51rb2 NXP Semiconductors, p89cv51rb2 Datasheet - Page 32

• Manufacturer Part Number: p89cv51rb2
• Description: P89cv51rb2/rc2/rd2 8-bit 80c51 5 V Low Power 64 Kb Flash Microcontroller With 1 Kb Ram, Spi, 6-clock Cpu With 6/12-clock Peripherals
• Manufacturer: NXP Semiconductors

NXP Semiconductors
P89CV51RB2_RC2_RD2_1
Product data sheet
6.5.3 Programmable clock-out
6.5.4 Baud rate generator mode
A 50 % duty cycle clock can be programmed to come out on pin T2 (P1[0], Clock-out
mode). This pin, besides being a regular I/O pin, has two additional functions. It can be
programmed:
To configure the timer/counter 2 as a clock generator, bit C/T2 (in T2CON) must be
cleared and bit T2OE in T2MOD must be set. Bit TR2 (T2CON.2) also must be set to start
the timer.
The clock-out frequency depends on the oscillator frequency and the reload value of
Timer 2 capture registers (RCAP2H, RCAP2L) as shown in
Where (RCAP2H, RCAP2L) = the content of RCAP2H and RCAP2L taken as a 16-bit
unsigned integer.
In the Clock-out mode, Timer 2 roll-overs will not generate an interrupt. This is similar to
when it is used as a baud rate generator.
Bits TCLK and/or RCLK in T2CON allow the UART transmit and receive baud rates to be
derived from either Timer 1 or Timer 2; see
1 is used as the UART transmit baud rate generator. When TCLK = 1, Timer 2 is used as
the UART transmit baud rate generator. RCLK has the same effect for the UART receive
baud rate. With these two bits, the serial port can have different receive and transmit baud
rates – Timer 1 or Timer 2.
Figure 14
------------------------------------------------------------------------------------------
2
1. To input the external clock for timer/counter 2, or
2. To output a 50 % duty cycle clock ranging from 122 Hz to 8 MHz at a 16 MHz
Fig 14. Timer 2 in Baud rate generator mode
operating frequency.
65536
T2 pin
OSC
OscillatorFrequency
shows Timer 2 in Baud rate generator mode:
–
T2EX pin
RCAP2H RCAP2L
2
transition
detector
Rev. 01 — 5 October 2007
C/T2 = 0
C/T2 = 1
EXEN2
control
TR2
P89CV51RB2/RC2/RD2
control
Section 6.6
EXF2
RCAP2L RCAP2H
(8-bits)
timer 2
interrupt
TL2
for details. When TCLK = 0, Timer
Equation
(8-bits)
TH2
80C51 with 1 kB RAM, SPI
reload
2:
© NXP B.V. 2007. All rights reserved.
TX/RX baud rate
002aaa526
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