AT89LP6440-20AU Atmel, AT89LP6440-20AU Datasheet - Page 86

• Manufacturer Part Number: AT89LP6440-20AU
• Description: MCU 8051 64K FLASH ISP 44TQFP
• Manufacturer: Atmel
• Series: 89LPr

Specifications of AT89LP6440-20AU

• Core Processor: 8051
• Core Size: 8-Bit
• Speed: 20MHz
• Connectivity: I²C, SPI, UART/USART
• Peripherals: Brown-out Detect/Reset, POR, PWM, WDT
• Number Of I /o: 38
• Program Memory Size: 64KB (64K x 8)
• Program Memory Type: FLASH
• Eeprom Size: 8K x 8
• Ram Size: 4.25K x 8
• Voltage - Supply (vcc/vdd): 2.4 V ~ 3.6 V
• Data Converters: A/D 8x10b
• Oscillator Type: Internal
• Operating Temperature: -40°C ~ 85°C
• Package / Case: 44-TQFP, 44-VQFP
• Package: 44TQFP
• Device Core: 8051
• Family Name: 89LP
• Maximum Speed: 20 MHz
• Operating Supply Voltage: 2.5|3.3 V
• Data Bus Width: 8 Bit
• Number Of Programmable I/os: 38
• Interface Type: 2-Wire/SPI
• On-chip Dac: 8-chx10-bit
• Number Of Timers: 3
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

16.2
16.2.1
86
Baud Rates
AT89LP6440 - Preliminary
Using Timer 1 to Generate Baud Rates
The baud rate in Mode 0 depends on the value of the SMOD1 bit in Special Function Register
PCON.7. If SMOD1 = 0 (the value on reset) and TB8 = 0, the baud rate is 1/4 of the oscillator
frequency. If SMOD1 = 1 and TB8 = 0, the baud rate is 1/2 of the oscillator frequency, as shown
in the following equation:
The baud rate in Mode 2 also depends on the value of the SMOD1 bit. If SMOD1 = 0, the baud
rate is 1/32 of the oscillator frequency. If SMOD1 = 1, the baud rate is 1/16 of the oscillator fre-
quency, as shown in the following equation:
Setting TB8 = 1 in Mode 0 enables Timer 1 as the baud rate generator. When Timer 1 is the
baud rate generator for Mode 0, the baud rates are determined by the Timer 1 overflow rate and
the value of SMOD1 according to the following equation:
The Timer 1 overflow rate normally 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.
Table 16-2
lists commonly used baud rates and how they can be obtained from Timer 1.
Modes 1, 3
Baud Rate
Mode 0 Baud Rate
Modes 1, 3
Baud Rate
Mode 0 Baud Rate
Mode 2 Baud Rate
Modes 1, 3
Baud Rate
TB8 = 1
TB8 = 0
=
=
2
------------------- -
2
------------------- -
SMOD1
=
SMOD1
32
32
2
------------------- -
=
SMOD1
32
=
=
2
------------------- -
×
×
SMOD1
2
------------------- -
2
------------------- -
-------------------------------------------------------- -
[
SMOD1
SMOD1
Oscillator Frequency
------------------------------------------------------ -
Oscillator Frequency
4
65536
32
×
4
[
(Timer 1 Overflow Rate)
256
×
×
×
–
(Timer 1 Overflow Rate)
–
(
Oscillator Frequency
Oscillator Frequency
RH1,RL1
(
TH1
)
]
)
]
×
×
-------------------- -
TPS
-------------------- -
TPS
1
1
+
+
1
1
3706A–MICRO–9/09