AT89LP4052 Atmel Corporation, AT89LP4052 Datasheet - Page 33

• Manufacturer Part Number: AT89LP4052
• Manufacturer: Atmel Corporation

Specifications of AT89LP4052

• Flash (kbytes): 4 Kbytes
• Max. Operating Frequency: 20 MHz
• Cpu: 8051-1C
• Max I/o Pins: 15
• Spi: 1
• Uart: 1
• Sram (kbytes): 0.25
• Operating Voltage (vcc): 2.4 to 5.5
• Timers: 2
• Isp: SPI
• Watchdog: Yes

18.2
18.2.1
3547J–MICRO–10/09
Baud Rates
Using Timer 1 to Generate Baud Rates
The baud rate in Mode 0 is fixed as shown in the following equation.
The baud rate in Mode 2 depends on the value of the SMOD1 bit in Special Function Register
PCON.7. If SMOD1 = 0 (the value on reset), the baud rate is 1/32 of the oscillator frequency. If
SMOD1 = 1, the baud rate is 1/16 of the oscillator frequency, as shown in the following equation.
The Timer 1 overflow rate determines the baud rates in Modes 1 and 3. When Timer 1 is the
baud rate generator, the baud rates are determined by the Timer 1 overflow rate and the value
of SMOD1 according to the following equation.
The Timer 1 interrupt should be disabled in this application. The Timer itself can be configured
for either timer or counter operation in any of its 3 running modes. In the most typical applica-
tions, it is configured for timer operation in auto-reload mode (high nibble of TMOD = 0010B). In
this case, the baud rate is given by the following formula.
Programmers can achieve very low baud rates with Timer 1 by configuring the Timer to run as a
16-bit auto-reload timer (high nibble of TMOD = 0001B). In this case, the baud rate is given by
the following formula.
Mode 2 Baud Rate
Modes 1, 3
Baud Rate
Modes 1, 3
Baud Rate
Modes 1, 3
Baud Rate
Mode 0 Baud Rate
=
=
=
2
------------------- -
SMOD1
2
------------------- -
2
------------------- -
32
SMOD1
=
SMOD1
32
32
2
------------------- -
SMOD1
32
×
=
×
×
(Timer 1 Overflow Rate)
Oscillator Frequency
------------------------------------------------------ -
-------------------------------------------------------- -
[
Oscillator Frequency
------------------------------------------------------ -
Oscillator Frequency
65536
×
[
(Oscillator Frequency)
256
AT89LP2052/LP4052
–
2
–
(
RH1,RL1
(
TH1
)
]
)
]
33