SAA5X9X Datasheet, PDF (11/68 Pages) NXP Semiconductors – Economy teletext and TV microcontrollers

Philips Semiconductors
Economy teletext and TV microcontrollers
Preliminary specification
SAA5x9x family
7.3.5 6-BIT PWM DACS
Eight 6-bit DACs are available to allow direct control of analog parts of the television.
Each low resolution 6-bit DAC is controlled by its associated Special Function Register (PWM0 to PWM7). The PWM
outputs are alternative functions of Port 2 and Port 3.4. The PWE bit in the SFR for the port corresponding to the PWM
should be set to logic 1 for correct operation of the PWM, e.g. if PWM0 is to be used, P2.1 should be set to logic 1 setting
the port pin to high-impedance.
7.3.5.1 Pulse Width Modulator Registers (PWM0 to PWM7)
Table 3 Pulse Width Modulator Registers (see Table 10 for addresses)
7
6
PWE
−
5
4
3
2
1
0
PV5
PV4
PV3
PV2
PV1
PV0
Table 4 Description of PWMn bits (n = 0 to 7)
BIT
SYMBOL
DESCRIPTION
7
PWE If PWE is set to a logic 1, the corresponding PWM is active and controls its assigned
port pin. If PWE is set to a logic 0, the port pin is controlled by the corresponding bit in
the port SFR.
6
−
Not used.
5
PV5
The output of the PWM is a pulse of period 21.33 µs with a pulse HIGH time determined
4
PV4
by the binary value of these 6-bits multiplied by 0.33 µs. PV5 is the most significant bit.
3
PV3
2
PV2
1
PV1
0
PV0
1997 Jul 07
11