AT89LP51ED2-20MU Atmel, AT89LP51ED2-20MU Datasheet - Page 94

• Manufacturer Part Number: AT89LP51ED2-20MU
• Description: 8-bit Microcontrollers - MCU 64KB 20MHz 2.4V-5.5V
• Manufacturer: Atmel

Specifications of AT89LP51ED2-20MU

• Rohs: yes
• Core: 8051
• Data Bus Width: 8 bit
• Maximum Clock Frequency: 20 MHz
• Program Memory Size: 64 KB
• Data Ram Size: 256 B
• On-chip Adc: Yes
• Operating Supply Voltage: 2.4 V to 5.5 V
• Operating Temperature Range: - 40 C to + 85 C
• Package / Case: VQFN-44
• Mounting Style: SMD/SMT
• Data Rom Size: 4 KB
• Interface Type: 2-Wire, SPI, UART
• Number Of Programmable I/os: 36
• Number Of Timers: 3
• Processor Series: AT89x
• Program Memory Type: Flash
• Factory Pack Quantity: 360

14.3.2
94
AT89LP51RD2/ED2/ID2 Preliminary
Up or Down Counter
Figure 14-3. Timer 2 Waveform: Auto-Reload Mode (DCEN = 0)
Setting DCEN = 1 enables Timer 2 to count up or down, as shown in
the T2EX pin controls the direction of the count (if EXEN2 = 1). A logic 1 at T2EX makes Timer 2
count up. When T2CM
also causes BOTTOM, the 16-bit value in RCAP2H and RCAP2L, to be reloaded into the timer
registers, TH2 and TL2, respectively. A logic 0 at T2EX makes Timer 2 count down. The timer
underflows when TH2 and TL2 equal BOTTOM, the 16-bit value stored in RCAP2H and
RCAP2L. The underflow sets the TF2 bit and causes MAX to be reloaded into the timer regis-
ters. The EXF2 bit toggles whenever Timer 2 overflows or underflows and can be used as a 17th
bit of resolution. In this operating mode, EXF2 does not flag an interrupt.
The behavior of Timer 2 when DCEN is enabled is shown in
flow/underflow rate for up-down counting mode is the same as for up counting mode, provided
that the count direction does not change. Changes to the count direction may result in longer or
shorter periods between time-outs.
Figure 14-4. Timer 2 Waveform: Auto-Reload Mode (DCEN = 1)
BOTTOM
BOTTOM
T2EX
EXF2
MAX
MAX
MIN
MIN
1-0
= 00B, the timer will overflow at MAX and set the TF2 bit. This overflow
Figure
Figure
14-4. The timer over-
14-5. In this mode,
TF2 Set
TF2 Set
3714A–MICRO–7/11