STC micro STC8A8K64D4 Series - Page 538

STC8A8K64D4 Series Manual
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[7: 0]} are reloaded into {EPCnL, CCAPnL [7: 0]}. This makes it possible to update the PWM without interference.
PWM frequency in 8-bit mode＝
PCA input clock source frequency
256
When EPCnH=0 and CCAPnH=00H, PWM fixed output high
When EPCnH=1 and CCAPnH=FFH, PWM fixed output low
The structure of PCA module working in 8-bit PWM mode is shown below.
PCA 8-bit PWM mode
0 0 0
Output 0
0 CL[7:0]
EPCnL CCAPnL[7:0]
0 0
9-bit comparator
enable
CL overflow
CCPn
1
EPCnH CCAPnH[7:0]
reload
CCAPMn
- ECOMn CAPPn CAPNn MATn TOGn PWMn ECCFn
Output 1
{0,CL[7:0]}<{EPCnL,CCAPnL[7:0]}
{0,CL[7:0]} >= {EPCnL,CCAPnL[7:0]}
18.3.4.2 7-bit PWM Mode
When EBSn [1:0] in the PCA_PWMn register is set to 01, the PCAn operates in 7-bit PWM mode, where {0, CL
[6: 0]} is compared with the capture registers {EPCnL, CCAPnL [6: 0]}. When PCA modules are operating in 7-bit
PWM mode, the output frequencies of them are the same because all the modules share a single PCA counter. The
output duty ratio of each module is set using the registers {EPCnL, CCAPnL [6: 0]}. The output is low when the value
of {0, CL [6: 0]} is less than {EPCnL, CCAPnL [6: 0]}, and the output is high when the value of {0, CL [6: 0]} is equal
to or greater than {EPCnL , CCAPnL [6: 0]}. When CL [6: 0] overflows from 7F to 00, the contents of {EPCnH,
CCAPnH [6: 0]} are reloaded into {EPCnL, CCAPnL [6: 0]}. This makes it possible to update the PWM without
interference.
PWM frequency in 7-bit mode＝
PCA input clock source frequency
128
When EPCnH=0 and CCAPnH=00H, PWM fixed output high
When EPCnH=1 and CCAPnH=FFH, PWM fixed output low
The structure of PCA module working in 7-bit PWM mode is shown below.