P89V51RD2 Philips Semiconductors, P89V51RD2 Datasheet - Page 33

• Manufacturer Part Number: P89V51RD2
• Description: 8-bit 80C51 5 V low power 64 kB Flash microcontroller with 1 kB RAM
• Manufacturer: Philips Semiconductors

Philips Semiconductors
9397 750 12964
Product data
Fig 14. Timer 2 in Baud Rate Generator mode.
OSC
T2 pin
7.4.4 Baud rate generator mode
T2EX pin
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
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 14
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:
---------------------------------------------------------------------------------------- -
2
¸
2
Modes 1 and 3 Baud Rates = Timer 2 Overflow Rate/16
transition
detector
65536
OscillatorFrequency
shows Timer 2 in baud rate generator mode:
C/T2 = 0
C/T2 = 1
RCAP2H RCAP2L
1
, Timer 2 is used as the UART transmit baud rate generator. RCLK
EXEN2
Rev. 01 — 01 March 2004
control
TR2
control
EXF2
interrupt
RCAP2L RCAP2H
Timer 2
(8-bits)
TL2
8-bit microcontrollers with 80C51 core
(8-bits)
TH2
reload
Section 7.5 “UARTs” on page 35
© Koninklijke Philips Electronics N.V. 2004. All rights reserved.
TX/RX baud rate
002aaa526
P89V51RD2
1
6
the oscillator
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for
(2)