Rainbow Electronics AT89LP216 - Manual (Page 34)

34
3621A–MICRO–6/06
AT89LP216 [Preliminary]
Figure 14-7. Timer/Counter 1 PWM Mode 1
14.5.3 Mode 2 – 8-bit Frequency Generator
Timer 0 in PWM Mode 2 functions as an 8-bit Auto-Reload timer, the same as normal Mode 2,
with the exception that the output pin T0 is toggled at every TL0 overflow (see
Figure 14-8 ).
Timer 1 in PWM Mode 2 is identical to Timer 0. PWM Mode 2 can be used to output a square
wave of varying frequency. THx acts as an 8-bit counter. The following formula gives the output
frequency for Timer 0 in PWM Mode 2.
Figure 14-8. Timer/Counter 1 PWM Mode 2
Note: {RH0 & RL0}/{RH1 & RL1} are not required by Timer 0/Timer 1 during PWM Mode 2 and may be
used as temporary storage registers.
OSC
TR1
GATE
INT1 Pin
TL1
(8 Bits)
Control
TH1
(8 Bits)
OCR1
RH1
(8 Bits)
=
T1
RL1
(8 Bits)
÷TPS
Mode 2:
f
out
Oscillator Frequency
2 256
TH
0 –
( ) ×
-------------------------------------------------------
1
TPS
1 +
-------------------- ×
=
OSC
TR1
GATE
INT1 Pin
TL1
(8 Bits)
Control
T1
TH1
(8 Bits)
÷TPS