TS80C52zzz-MIC Atmel Corporation, TS80C52zzz-MIC Datasheet - Page 13

• Manufacturer Part Number: TS80C52zzz-MIC
• Description: 8-bit Microcontroller 8 Kbytes ROM/OTP, ROMless
• Manufacturer: Atmel Corporation

Figure 4. Auto-reload Mode Up/Down Counter (DCEN = 1)
4184E–8051–09/02
Programmable Clock-output
XTAL1
F
XTAL
In the clock-out mode, timer 2 operates as a 50%-duty-cycle, programmable clock gen-
erator (See Figure 5) . The input clock increments TL2 at frequency F
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
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.
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
F
Clock OutFrequency
OSC
–
(UP COUNTING RELOAD VALUE)
(:6 in X2 mode)
(DOWN COUNTING RELOAD
OSC
T2
:12
RCAP2L
(8-bit)
(8-bit)
/4). The generated clock signal is brought out to T2 pin (P1.0).
(8-bit)
TL2
FFh
T2CONreg
RCAP2H
C/T2
(8-bit)
(8-bit)
TH2
(8-bit)
0
FFh
1
=
------------------------------------------------------------------------------------------- -
4
×
(
65536 RCAP2H
T2CONreg
TR2
–
T2EX:
if DCEN=1, 1=UP
if DCEN=1, 0=DOWN
if DCEN = 0, up counting
T2CONreg
TOGGL
F
TF2
osc
T2CONreg
EXF2
⁄
INTERRUPT
RCAP2L
TIMER 2
TS8xCx2X2
OSC
)
/2. The timer
13