AT89LP51RD2 Atmel Corporation, AT89LP51RD2 Datasheet - Page 95

• Manufacturer Part Number: AT89LP51RD2
• Manufacturer: Atmel Corporation

Specifications of AT89LP51RD2

• Flash (kbytes): 64 Kbytes
• Max. Operating Frequency: 20 MHz
• Cpu: 8051-1C
• Max I/o Pins: 42
• Spi: 1
• Twi (i2c): 1
• Uart: 1
• Adc Channels: 7
• Adc Resolution (bits): 10
• Adc Speed (ksps): 153.8
• Sram (kbytes): 2.25
• Self Program Memory: API
• Operating Voltage (vcc): 2.4 to 5.5
• Timers: 4
• Isp: SPI/OCD/UART
• Watchdog: Yes

14.4
3714A–MICRO–7/11
Baud Rate Generator
Figure 14-5. Timer 2 Diagram: Auto-Reload Mode (DCEN = 1)
Timer 2 is selected as the baud rate generator by setting TCLK and/or RCLK in T2CON
14-3). Note that the baud rates for transmit and receive can be different if Timer 2 is used for the
receiver or transmitter and Timer 1 is used for the other function. Setting RCLK and/or TCLK
puts Timer 2 into its baud rate generator mode, as shown in
The baud rate generator mode is similar to 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.
The baud rates in UART Modes 1 and 3 are determined by Timer 2’s overflow rate according to
the following equation.
The Timer can be configured for either timer or counter operation. In most applications, it is con-
figured for timer operation (CP/T2 = 0). The baud rate formulas are given below.
where (RCAP2H, RCAP2L) is the content of RCAP2H and RCAP2L taken as a 16-bit unsigned
integer.
Timer 2 as a baud rate generator is shown in
TCLK = 1 in T2CON. Note that a rollover in TH2 does not set TF2 and will not generate an inter-
rupt. Note too, that if EXEN2 is set, a 1-to-0 transition in T2EX will set EXF2 but will not cause a
reload from (RCAP2H, RCAP2L) to (TH2, TL2). Thus when Timer 2 is in use as a baud rate gen-
erator, T2EX can be used as an extra external interrupt. Also note that the Baud Rate and
Frequency Generator modes may be used simultaneously.
CLK
SYS
÷TPS
Modes 1 and 3 Baud Rates
Modes 1, 3
Baud Rate
AT89LP51RD2/ED2/ID2 Preliminary
=
---------------------------------------------------------------------------------------------- -
16
×
[
65536
Figure
=
–
Timer 2 Overflow Rate
----------------------------------------------------------- -
(
RCAP2H,RCAP2L
f
SYS
14-6. This figure is valid only if RCLK or
Figure
16
14-6.
)
]
(Table
95