W78C354 Datasheet, PDF (27/44 Pages) Winbond – MONITOR MICROCONTROLLER

W78C354
L. PWM DACs
There are two 12-bit and fourteen 8-bit PWM static DACs and one 12-bit and three 8-bit PWM
dynamic DACs on this chip. The number of the PWM outputs is different with the package.
68-PIN PLCC
48-PIN DIP
40-PIN DIP
8-bit SDAC
12-bit SDAC
8-bit DDAC
14
8 + 4*
8 + 4*
2
1
1
3
3
1
12-bit DDAC
1
1
1
Note : 4* : the SDACS share with P2.4~P2.7
L-1.1 14-channel 8-bit PWM Static DAC
The static DACs (SDAC0 to 13) are used to generate DC voltage control (0 to 5V) by an RC circuit,
as shown in Figure 8, and to execute the "MOV SDACn, #Value" instruction. There are 14 registers,
corresponding to the 14 channels of 8-bit PWM output. The unused PWM channel can be used as an
output pin, since 0 or 5V can be obtained from the pin.
• Duty cycle of the PWM output = Preset value of SDACn ¡Ò 255, where n = 0 to 13
• DC voltage after low-pass filter = VCC × duty cycle
• SDAC0−SDAC13: 8-bit PWM static DAC registers storing preset values
PRESET VALUE
0
1
n
255
DUTY CYCLE
0/255
1/255
n/255
255/255
DC VOLTAGE
0V
1/255 × 5V
n/255 × 5V
+5V
• PWM frequency FPWM = FCLOCK ¡Ò 255
Fclock
16 MHz
FPWM
62.745 KHz
TPWM
15.94 µS
18.432 MHz
72.282 KHz
13.83 µS
20 MHz
78.431 KHz
12.75 µS
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Publication Release Date: October 1996
Revision A1