T89C51CC02 Atmel, T89C51CC02 Datasheet - Page 59

• Manufacturer Part Number: T89C51CC02
• Description: 8-Bit MCU
• Manufacturer: Atmel

13.3. Programmable Clock-Output
In clock-out mode, timer 2 operates as a 50%-duty-cycle, programmable clock generator (See Figure 46). The input
clock increments TL2 at frequency F
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 depending on the system oscillator
frequency and the value in the RCAP2H and RCAP2L registers:
NOTE: X2 bit is located in CKCON register.
In X2 mode, F
For a 16 MHz system clock, timer 2 has a programmable frequency range of 61 Hz (F
4). The generated clock signal is brought out to T2 pin (P1.0).
Timer 2 is programmed for the clock-out mode as follows:
Rev.A - May 17, 2001
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.
T2
OSC
=F
XTAL
. In standard mode, F
CLOCK
Clock OutFrequency
FT2
–
Figure 45. Auto-Reload Mode Up/Down Counter
:
OSC
6
OSC
=F
XTAL
/2. The timer repeatedly counts to overflow from a loaded value. At
Preliminary
/2.
=
T2CON.1
CT/2
--------------------------------------------------------------------------------------
4
0
1
(UP COUNTING RELOAD VALUE)
(DOWN COUNTING RELOAD VALUE)
65536 RCAP2H
RCAP2L
(8-bit)
(
(8-bit)
TL2
FFh
8-bit)
–
F
osc
RCAP2H
(
(8-bit)
TH2
8-bit)
(8-bit)
FFh
2 x2
RCAP2L
T89C51CC02
T2CON.2
TR2
OSC
T2EX:
1=UP
2=DOWN
T2CONreg
TOGGLE
/2
TF2
16)
to 4 MHz (F
T2CONreg
EXF2
INTERRUPT
TIMER 2
OSC
59
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