AT89LP51ED2 Atmel Corporation, AT89LP51ED2 Datasheet - Page 93

• 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

14.3
14.3.1
3714A–MICRO–7/11
Auto-Reload Mode
Up Counter
Timer 2 can be programmed to count up or down when configured in its 16-bit auto-reload
mode. This feature is invoked by the DCEN (Down Counter Enable) bit located in the SFR
T2MOD (see
count up. When DCEN is set, Timer 2 can count up or down, depending on the value of the
T2EX pin. A summary of the Auto-Reload behaviors is listed in
Table 14-5.
Figure 14-2
counts up to MAX and then sets the TF2 bit upon overflow. The overflow also causes the timer
registers to be reloaded with BOTTOM, the 16-bit value in RCAP2H and RCAP2L. If EXEN2 = 1,
a 16-bit reload can be triggered either by an overflow or by a 1-to-0 transition at external input
T2EX. This transition also sets the EXF2 bit. Both the TF2 and EXF2 bits can generate an inter-
rupt. The Timer 2 overflow rate for this mode is given in the following equation:
Note:
Figure 14-2. Timer 2 Diagram: Auto-Reload Mode (DCEN = 0)
DCEN
0
1
1
Auto-Reload Mode:
In Fast Mode, TPS applies only when the T2X2 bit in CKCON0 is set. TPS always
applies in Compatibility Mode, therefore setting T2X2 in Compatibility Mode will double
the timeout period.
DCEN = 0
CLK
shows Timer 2 automatically counting up when DCEN = 0. In this mode Timer 2
SYS
T2EX
Table
X
Summary of Auto-Reload Modes
0
1
÷TPS
14-4). Upon reset, the DCEN bit is set to 0 so that timer 2 will default to
Direction
Down
Up
Up
AT89LP51RD2/ED2/ID2 Preliminary
Time-out Period
Behavior
BOTTOM
MAX
BOTTOM
→
BOTTOM
→
→
MAX
MAX
=
65536
------------------------------------------------------------------------------ -
reload to BOTTOM
underflow to MAX
overflow to BOTTOM
–
TL2
{
RCAP2H RCAP2L
f
Table
SYS
TH2
,
14-5.
}
×
(
TPS
+
1
)
93