AT80C51RD2 Atmel Corporation, AT80C51RD2 Datasheet - Page 18

• Manufacturer Part Number: AT80C51RD2
• Manufacturer: Atmel Corporation

Specifications of AT80C51RD2

• Max. Operating Frequency: 60 MHz
• Cpu: 8051-12C
• Max I/o Pins: 32
• Spi: 1
• Uart: 1
• Sram (kbytes): 1.25
• Operating Voltage (vcc): 2.7 to 5.5
• Timers: 4
• Watchdog: Yes

Figure 9-1.
9.2
18
Programmable Clock-Output
AT80C51RD2
F
Auto-Reload Mode Up/Down Counter (DCEN = 1)
CLK PERIPH
In the clock-out mode, Timer 2 operates as a 50% duty-cycle, programmable clock generator
(see Figure 9-2). The input clock increments TL2 at frequency F
edly 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 inter-
rupts. 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
(P1.0).
Timer 2 is programmed for the clock-out mode as follows:
• 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
• Enter a 16-bit initial value in timer registers TH2/TL2. It can be the same as the reload value
• To start the timer, set TR2 run control bit in T2CON register.
CLK PERIPH
registers.
or a different one depending on the application.
/2
16)
to 4 MHz (F
Clock OutFrequency
:6
–
(UP COUNTING RELOAD VALUE)
CLK PERIPH
(DOWN COUNTING RELOAD VALUE)
RCAP2L
T2
(8-bit)
(8-bit)
(8-bit)
TL2
FFh
/4). The generated clock signal is brought out to T2 pin
T2CON
=
RCAP2H
C/T2
(8-bit)
(8-bit)
TH2
(8-bit)
0
FFh
1
---------------------------------------------------------------------------------------- -
4
×
(
65536 RCAP2H
T2CON
TR2
F
–
CLKPERIPH
T2EX:
if DCEN = 1, 1 = UP
if DCEN = 1, 0 = DOWN
if DCEN = 0, up counting
T2CON
TOGGLE
TF2
CLK PERIPH
⁄
RCAP2L
T2CON
EXF2
INTERRUPT
TIMER 2
/2. The timer repeat-
)
4113D–8051–01/09