AT89C5131-PLTIL ATMEL Corporation, AT89C5131-PLTIL Datasheet - Page 50

• Manufacturer Part Number: AT89C5131-PLTIL
• Description: 8-bit Flash Microcontroller with Full Speed USB Device
• Manufacturer: ATMEL Corporation

Figure 23. Auto-reload Mode Up/Down Counter (DCEN = 1)
Programmable Clock
Output
50
AT89C5131
F
CLK PERIPH
In the Clock-out mode, Timer 2 operates as a 50%-duty-cycle, programmable clock gen-
erator (See Figure 24). 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 following formula gives the Clock-out fre-
quency 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:
•
•
•
•
•
CLK PERIPH
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
: 6
Clock OutFrequency
16)
to 4 MHz (F
(UP COUNTING RELOAD VALUE)
(DOWN COUNTING RELOAD VALUE)
–
RCAP2L
T2
(8-bit)
(8-bit)
(8-bit)
TL2
FFh
CLK PERIPH
T2CON
RCAP2H
C/T2
(8-bit)
(8-bit)
TH2
(8-bit)
0
FFh
1
=
/4). The generated clock signal is brought out to
---------------------------------------------------------------------------------------- -
4
T2CON
65536 RCAP2H
TR2
F
–
CLKPERIPH
T2EX:
if DCEN = 1, 1 = UP
if DCEN = 1, 0 = DOWN
if DCEN = 0, up counting
T2CON
TOGGLE
TF2
T2CON
EXF2
INTERRUPT
RCAP2L
Timer 2
CLK PERIPH
4136B–USB–09/03
/2. The