参数资料
型号: SAA5491H/NNN
厂商: NXP SEMICONDUCTORS
元件分类: 微控制器/微处理器
英文描述: 8-BIT, MROM, 12 MHz, MICROCONTROLLER, PQFP80
封装: 14 X 20 MM, 2.80 MM HEIGHT, PLASTIC, SOT-318-2, QFP-80
文件页数: 5/72页
文件大小: 498K
代理商: SAA5491H/NNN
1998 Dec 14
13
Philips Semiconductors
Preliminary specication
Economy teletext and TV microcontrollers
SAA5x9x family
7.3.6
14-BIT PWM DAC
One 14-bit DAC is available to allow direct control of
analog sections of the television. The 14-bit PWM is
controlled using Special Function Registers TDACL and
TDACH.
The output of the TPWM is a pulse of period 42.66
s.
The 7 most significant bits, TDACH.TD13 (MSB) to
TDACH.TD8 and TDACL.TD7, alter the pulse width
between 0 and 42.33
s, in much the same way as in the
6-bit PWMs.
The 7 least significant bits, TDACL.TD6 to TDACL.TD0
(LSB), extend certain pulses by a further 0.33
s, e.g. if the
7 least significant bits are given the value 01H, then
1 in 128 cycles is extended. If the 7 least significant bits
are given the value 02H, then 2 in 128 cycles is extended,
and so forth.
The TPWM will not start to output a new value until after
writing a value to TDACH. Therefore, if the value is to be
changed, TDACL should be written to before TDACH.
7.3.6.1
TPWM High Byte Register (TDACH)
Table 5
TPWM High Byte Register (SFR address D3H)
Table 6
Description of TDACH bits
7.3.6.2
TPWM Low Byte Register (TDACL)
Table 7
TPWM Low Byte Register (SFR address D2H)
Table 8
Description of TDACL bits
76543210
PWE
TD13
TD12
TD11
TD10
TD9
TD8
BIT
SYMBOL
DESCRIPTION
7
PWE
If PWE is set to a logic 1, the TPWM is active and controls port line P2.0. 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
TD13
These 6-bits along with bit TD7 in the TDACL register control the pulse width period.
TD13 is the most signicant bit.
4
TD12
3
TD11
2
TD10
1
TD9
0
TD8
76543210
TD7
TD6
TD5
TD4
TD3
TD2
TD1
TD0
BIT
SYMBOL
DESCRIPTION
7
TD7
This bit is used with bits TD13 to TD8 in the TDACH register to control the pulse width
period.
6 to 0
TD6 to TD0
These 7-bits extend certain pulses by a further 0.33
s.
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