TS80C54X2YYY-MICD Atmel Corporation, TS80C54X2YYY-MICD Datasheet - Page 14

• Manufacturer Part Number: TS80C54X2YYY-MICD
• Description: 8-bit CMOS Microcontroller 16/32 Kbytes ROM/OTP
• Manufacturer: Atmel Corporation

TS80C54X2/C58X2
TS87C54X2/C58X2
6.3.2 Programmable Clock-Output
In the clock-out mode, timer 2 operates as a 50%-duty-cycle, programmable clock generator (See Figure 5) . The
input clock increments TL2 at frequency F
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
Timer 2 is programmed for the clock-out mode as follows:
14
OSC
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)
to 4 MHz (F
XTAL1
Clock OutFrequency
F
OSC
Figure 4. Auto-Reload Mode Up/Down Counter (DCEN = 1)
XTAL
/4). The generated clock signal is brought out to T2 pin (P1.0).
–
OSC
F
OSC
/2. The timer repeatedly counts to overflow from a loaded value.
=
--------------------------------------------------------------------------------------
4
(UP COUNTING RELOAD VALUE)
(:6 in X2 mode)
(DOWN COUNTING RELOAD VALUE)
65536 RCAP2H
T2
:
12
RCAP2L
(8-bit)
(8-bit)
(8-bit)
TL2
FFh
–
F
osc
T2CONreg
RCAP2H
C/T2
(8-bit)
(8-bit)
TH2
(8-bit)
0
FFh
1
RCAP2L
T2CONreg
TR2
Rev. C - 15 January, 2001
T2EX:
if DCEN=1, 1=UP
if DCEN=1, 0=DOWN
if DCEN = 0, up counting
TOGGLE
T2CONreg
TF2
T2CONreg
EXF2
INTERRUPT
TIMER 2