AT89LP428-20AU Atmel, AT89LP428-20AU Datasheet - Page 79

• Manufacturer Part Number: AT89LP428-20AU
• Description: MCU 8051 4K FLASH SPI 32TQFP
• Manufacturer: Atmel
• Series: 89LPr

Specifications of AT89LP428-20AU

• Core Processor: 8051
• Core Size: 8-Bit
• Speed: 20MHz
• Connectivity: SPI, UART/USART
• Peripherals: Brown-out Detect/Reset, POR, PWM, WDT
• Number Of I /o: 30
• Program Memory Size: 4KB (4K x 8)
• Program Memory Type: FLASH
• Eeprom Size: 512 x 8
• Ram Size: 768 x 8
• Voltage - Supply (vcc/vdd): 2.4 V ~ 5.5 V
• Oscillator Type: Internal
• Operating Temperature: -40°C ~ 85°C
• Package / Case: 32-TQFP, 32-VQFP
• Processor Series: AT89x
• Core: 8051
• 3rd Party Development Tools: PK51, CA51, A51, ULINK2
• Development Tools By Supplier: AT89ISP
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Data Converters: -
• Lead Free Status / Rohs Status: Details

16.2
16.2.1
3654A–MICRO–8/09
Baud Rates
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:
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
------------------- -
=
SMOD1
32
2
------------------- -
SMOD1
=
32
=
=
2
------------------- -
×
SMOD1
2
------------------- -
2
------------------- -
Oscillator Frequency
------------------------------------------------------ -
SMOD1
SMOD1
4
32
×
4
[
(Timer 1 Overflow Rate)
256
×
×
×
(Timer 1 Overflow Rate)
–
Oscillator Frequency
Oscillator Frequency
(
TH1
)
]
×
AT89LP428/828
-------------------- -
TPS
1
+
1
79