AT89LP6440-20AU Atmel, AT89LP6440-20AU Datasheet - Page 66

• 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

12.4
66
Baud Rate Generator
AT89LP6440 - Preliminary
Figure 12-7. Timer 2 Waveform: Dual Slope Modes
Timer 2 is selected as the baud rate generator by setting TCLK and/or RCLK in T2CON
12-3). 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-
T2CM = 01B
T2CM = 00B
EXF2
MAX
MAX
TOP
TOP
MIN
MIN
Modes 1 and 3 Baud Rates
Modes 1, 3
Modes 1, 3
Baud Rate
Baud Rate
=
=
------------------------------------------------------------------------------------------------------------------ -
16
-------------------------------------------------------------------------------------------------------------------------------- -
16
×
×
(
(
TPS
TPS
Figure
T2CM
T2CM
=
+
+
Oscillator Frequency
Timer 2 Overflow Rate
----------------------------------------------------------- -
1-0
1-0
1
1
Oscillator Frequency
12-8. This figure is valid only if RCLK or
)
)
= 10B
= 11B
×
×
[
[
(
65536
RCAP2H RCAP2L
Figure
16
–
12-8.
(
RCAP2H,RCAP2L
,
)
+
TF2 Set
TF2 Set
3706A–MICRO–9/09
1
]
)
]
(Table