参数资料
型号: SST89V54RDA-33-C-QIF
元件分类: 微控制器/微处理器
英文描述: 8-BIT, FLASH, 33 MHz, MICROCONTROLLER, QCC40
封装: ROHS COMPLIANT, MO-220IWJJD-5, WQFN-40
文件页数: 52/84页
文件大小: 1755K
代理商: SST89V54RDA-33-C-QIF
56
Data Sheet
FlashFlex MCU
SST89E54RD2A/RDA / SST89E58RD2A/RDA
SST89V54RD2A/RDA / SST89V58RD2A/RDA
2007 Silicon Storage Technology, Inc.
S71339-01-000
1/07
8.3.4 Pulse Width Modulator
The Pulse Width Modulator (PWM) mode is used to gener-
ate 8-bit PWMs by comparing the low byte of the PCA
timer (CL) with the low byte of the compare register
(CCAPnL). When CL < CCAPnL the output is low. When
CL
≥ CCAPnL the output is high. To activate this mode, the
user must set the PWM and ECOM bits in the module’s
CCAPMn SFR. (See Figure 8-5 and Table 8-7)
In PWM mode, the frequency of the output depends on the
source for the PCA timer. Since there is only one set of CH
and CL registers, all modules share the PCA timer and fre-
quency. Duty cycle of the output is controlled by the value
loaded into the high byte (CCAPnH). Since writes to the
CCAPnH register are asynchronous, a new value written to
the high byte will not be shifted into CCAPnL for compari-
son until the next period of the output (when CL rolls over
from 255 to 00).
To calculate values for CCAPnH for any duty cycle, use
the following equation:
CCAPnH = 256(1 - Duty Cycle)
where CCAPnH is an 8-bit integer and Duty Cycle is a
fraction.
FIGURE
8-5: PCA Pulse Width Modulator Mode
TABLE
8-7: Pulse Width Modulator Frequencies
PCA Timer Mode
PWM Frequency
12 MHz
16 MHz
1/12 Oscillator Frequency
3.9 KHz
5.2 KHz
1/4 Oscillator Frequency
11.8 KHz
15.6 KHz
Timer 0 Overflow:
8-bit
15.5 Hz
20.3 Hz
16-bit
0.06 Hz
0.08 Hz
8-bit Auto-Reload
3.9 KHz to 15.3 Hz
5.2 KHz to 20.3 Hz
External Input (Max)
5.9 KHz
7.8 KHz
T8-7.0 1339
1339 F27.0
ECOMn CAPPn CAPNn
MATn
TOGn
PWMn ECCFn
CCAPMn
n=0 to 4
CL
CCAPnL
CCAPnH
PCA Timer/Counter
0
00
8-bit Comparator
Overflow
CL < CCAPnL
CL >= CCAPnL
Enable
CEXn
0
1
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