AT89LP51ED2 Atmel Corporation, AT89LP51ED2 Datasheet - Page 96

• Manufacturer Part Number: AT89LP51ED2
• Manufacturer: Atmel Corporation

Specifications of AT89LP51ED2

• 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
• Eeprom (bytes): 4096
• Self Program Memory: API
• Operating Voltage (vcc): 2.4 to 5.5
• Timers: 4
• Isp: SPI/OCD/UART
• Watchdog: Yes

14.5
96
Frequency Generator (Programmable Clock Out)
AT89LP51RD2/ED2/ID2 Preliminary
Figure 14-6. Timer 2 in Baud Rate Generator Mode
Timer 2 can generate a 50% duty cycle clock on T2 (P1.0). This pin, besides being a regular I/O
pin, has two alternate functions. It can be programmed to input the external clock for
Timer/Counter 2 or to toggle its output at every timer overflow. To configure the Timer/Counter 2
as a clock generator, bit C/T2 (T2CON.1) must be cleared and bit T2OE (T2MOD.1) must be
set. Bit TR2 (T2CON.2) starts and stops the timer. The clock-out frequency depends on the sys-
tem frequency and the reload value of Timer 2 capture registers (RCAP2H, RCAP2L), as shown
in the following equation.
In the frequency generator mode, Timer 2 roll-overs will not generate an interrupt. This behavior
is similar to when Timer 2 is used as a baud-rate generator. It is possible to use Timer 2 as a
baud-rate generator and a clock generator simultaneously. Note, however, that the baud-rate
and clock-out frequencies cannot be determined independently from one another since they
both use RCAP2H and RCAP2L.
Figure 14-7. Timer 2 in Clock-out Mode
T2EX PI N
T2 PI N
T2EX PIN
T2 PIN
CLK
TRANSITION
DETECT OR
SYS
Clock Out Frequency
C/T2 = 0
C/T2 = 1
CLK
TRANSITION
DETECTOR
SYS
EXEN2
TR2
=
------------------------------------------------------------------------------------------- -
2
C/T2
×
EXEN2
TR2
[
RCAP2L
65536
TL2
EXF2
–
RCAP2H
(
RCAP2H,RCAP2L
TH2
f
SYS
RCAP2L
TL2
÷2
EXF2
INTERR UPT
TIMER 2
RCAP2H
÷
TH2
2
"1"
"1"
TIMER 1 OVERFLOW
)
]
"0"
"0"
"0"
T2OE
INTERRUPT
TIMER 2
"1"
3714A–MICRO–7/11
÷
SMOD1
RCLK
TCLK
÷
16
16
CLOCK
CLOCK
Rx
Tx