AT89C51IC2 Atmel Corporation, AT89C51IC2 Datasheet - Page 31

• Manufacturer Part Number: AT89C51IC2
• Manufacturer: Atmel Corporation

Specifications of AT89C51IC2

• Flash (kbytes): 32 Kbytes
• Max. Operating Frequency: 60 MHz
• Cpu: 8051-12C
• Max I/o Pins: 34
• Spi: 1
• Twi (i2c): 1
• Uart: 1
• Sram (kbytes): 1.25
• Self Program Memory: API
• Operating Voltage (vcc): 2.7 to 5.5
• Timers: 4
• Isp: UART
• Watchdog: Yes

Figure 9. Auto-Reload Mode Up/Down Counter (DCEN = 1)
Programmable Clock-
Output
4301D–8051–02/08
F
CLK PERIPH
In the clock-out mode, timer 2 operates as a 50%-duty-cycle, programmable clock gen-
erator (See Figure 10). The input clock increments TL2 at frequency F
timer repeatedly counts to overflow from a loaded value. At overflow, the contents of
RCAP2H and RCAP2L registers are loaded into TH2 and TL2. In this mode, timer 2
overflows do not generate interrupts. The formula gives the clock-out frequency as a
function of the system oscillator frequency and the value in the RCAP2H and RCAP2L
registers:
For a 16 MHz system clock, timer 2 has a programmable frequency range of 61 Hz
(F
T2 pin (P1.0).
Timer 2 is programmed for the clock-out mode as follows:
•
•
•
•
•
It is possible to use timer 2 as a baud rate generator and a clock generator simulta-
neously. For this configuration, the baud rates and clock frequencies are not
independent since both functions use the values in the RCAP2H and RCAP2L registers.
CLK PERIPH
Clock OutFrequency
Set T2OE bit in T2MOD register.
Clear C/T2 bit in T2CON register.
Determine the 16-bit reload value from the formula and enter it in RCAP2H/RCAP2L
registers.
Enter a 16-bit initial value in timer registers TH2/TL2. It can be the same as the
reload value or a different one depending on the application.
To start the timer, set TR2 run control bit in T2CON register.
–
/2
16)
:6
to 4 MHz (F
(UP COUNTING RELOAD VALUE)
(DOWN COUNTING RELOAD VALUE)
RCAP2L
T2
(8-bit)
(8-bit)
(8-bit)
=
TL2
FFh
CLK PERIPH
---------------------------------------------------------------------------------------- -
4
×
(
T2CON
RCAP2H
C/T2
65536 RCAP2H
(8-bit)
(8-bit)
TH2
(8-bit)
0
FFh
1
/4). The generated clock signal is brought out to
F
–
CLKPERIPH
T2CON
TR2
T2EX:
if DCEN=1, 1=UP
if DCEN=1, 0=DOWN
if DCEN = 0, up counting
⁄
RCAP2L
T2CON
TOGGLE
TF2
)
T2CON
EXF2
INTERRUPT
TIMER 2
CLK PERIPH
/2. The
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