Intel MCS 51 User Manual

i~.
87C51GB HARDWARE DESCRIPTION
Table16.PWMFrequencies
PCATimerMode
PWMFrequenoy
12MHz
16MHz
1/12Osc.Frequency 3.9KHz
5.2KHz
1f4 Osc.
Frequency 11.8 KHz
15.6 KHz
TimerOOverflow:
8-bit
15.5Hz
16-bit
20.3HZ
0.06
iiz
0.08Hz
8-bitAuto-Reload
3.9KHzto15.3
Iiz
5.2 KHzto20.3tiz
ExternalInput(Max) 5.9KHz
7.8KHz
For this mode the ECOMnbit and the PWMn bits in The value in CCAPnL
controls the duty cycle of the
the CCAPMn mode register needto be set. The PCA waveform.To changethe value in CCAPnL without
generates8-bitPWMSbycomparingthe lowbyteofthe output glitches, the user must write to the high byte
PCA timer (CL) with the low byte of the module’s register(CCAPnH).Thisvalueis thenshiftedbyhard-
compare registers (CCAPnL).WhenCL < CCAPnL
wareinto CCAPnLwhenCL rolls overfromOFFIIto
the output is low.When CL > CCAPnLthe outrmtis OOHwhich correspondsto the next tied of the out-
high.R-eferto Figure 23. put.
z
CCAPnH
CL MADE
FF TO 00
IRANSillON
CCAPnL
.,09.
I
CLC CCAPnL
CL
CLZ CCAPnL
I
CEXnPIN
T
ENABLE
1
., ,,
w
CCAPMnMODEREGISTER
270887-25
Figure23.PCA6-BitPWMMode
6-32

Intel MCS 51 Specifications

General

Brand	Intel
Model	MCS 51
Category	Microcontrollers
Language	English