p87c770aar NXP Semiconductors, p87c770aar Datasheet - Page 31

• Manufacturer Part Number: p87c770aar
• Description: Microcontrollers Ntsc With On-screen Display Closed Caption
• Manufacturer: NXP Semiconductors

Philips Semiconductors
15 7-BIT PWM DAC
The P8xCx70 has nine PWM DAC outputs (PWM0 to PWM8) for analog control e.g. volume, balance, bass, treble,
brightness, contrast, sharpness, hue and saturation.
Each PWM output generates a pulse pattern with a repetition rate of
ratio of the HIGH-time and the repetition time. A DC voltage proportional to the PWM control setting is obtained by means
of an external integration network (low-pass filter). The polarity of each PWM output is fixed to active HIGH.
The HIGH-time of a PWMn output (within one PWM cycle time) may be calculated as shown in Equation (1).
Where PWMn is the contents of PWMn data latch; t
15.1
The alternative PWM functions of Port 0 pins are enabled by writing a logic 1 to the PWMnE bit of the associated Special
Function Register. When setting the PWMnE bit to a logic 0, the associated pin becomes a general I/O port line.
Table 39 SFR data registers for the 7-bit PWMs
1999 Jun 11
t
HIGH
REGISTER
Microcontrollers for NTSC TVs with On-Screen
Display (OSD) and Closed Caption (CC)
PWM0
PWM1
PWM2
PWM3
PWM4
PWM5
PWM6
PWM7
PWM8
=
SFRs for PWM output control
PWMn t
ADDRESS
0
A6H
B6H
C6H
D6H
E6H
86H
96H
F6H
F5H
PWM0E
PWM1E
PWM2E
PWM3E
PWM4E
PWM5E
PWM6E
PWM7E
PWM8E
7
data6
data6
data6
data6
data6
data6
data6
data6
data6
6
0
= 1/f
data5
data5
data5
data5
data5
data5
data5
data5
data5
5
PWM
31
and f
data4
data4
data4
data4
data4
data4
data4
data4
data4
PWM
4
1
128
=
f
PWM
1
4
f
xtal
data3
data3
data3
data3
data3
data3
data3
data3
data3
. The analog value is determined by the
3
.
data2
data2
data2
data2
data2
data2
data2
data2
data2
2
P8xCx70 family
Product specification
data1
data1
data1
data1
data1
data1
data1
data1
data1
1
data0
data0
data0
data0
data0
data0
data0
data0
data0
0
(1)