P89LV51RD2BA PHILIPS [NXP Semiconductors], P89LV51RD2BA Datasheet - Page 36

• Manufacturer Part Number: P89LV51RD2BA
• Description: 8-bit 80C51 3 V low power 64 kB Flash microcontroller with 1 kB RAM
• Manufacturer: PHILIPS [NXP Semiconductors]

Philips Semiconductors
9397 750 14342
Product data
Fig 15. Timer 2 in Baud Rate Generator mode.
OSC
T2 pin
7.4.4 Baud rate generator mode
T2EX pin
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
details). When TCLK = 0, Timer 1 is used as the UART transmit baud rate generator.
When TCLK =
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 15
The baud rate generation mode is like the auto-reload mode, when 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:
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.,
frequency). As a baud rate generator, it increments at the oscillator frequency. Thus
the baud rate formula is as follows:
Where: (RCAP2H, RCAP2L) = The content of RCAP2H and RCAP2L taken as a
16-bit unsigned integer.
----------------------------------------------------------------------------------------------- -
¸
16
2
Modes 1 and 3 Baud Rates = Timer 2 Overflow Rate/16
Modes 1 and 3 Baud Rates =
transition
detector
65536 RCAP2H RCAP2L
OscillatorFrequency
shows Timer 2 in baud rate generator mode:
C/T2 = 0
C/T2 = 1
–
1
, Timer 2 is used as the UART transmit baud rate generator. RCLK
EXEN2
Rev. 04 — 02 December 2004
control
TR2
control
EXF2
interrupt
RCAP2L RCAP2H
Timer 2
(8-bits)
P89LV51RB2/RC2/RD2
TL2
(8-bits)
8-bit microcontrollers with 80C51 core
TH2
reload
Section 7.5 “UARTs” on page 37
© Koninklijke Philips Electronics N.V. 2004. All rights reserved.
TX/RX baud rate
002aaa526
1
6
the oscillator
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for
(3)