P80C557E4 查看數據表（PDF） - Philips Electronics
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P80C557E4 Datasheet PDF : 72 Pages
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Philips Semiconductors
Single-chip 8-bit microcontroller
Product specification
P83C557E4/P80C557E4/P89C557E4
Digital Input Port Register P5
Port 5 Special Function Register P5 always represents the binary
value of the logic level at input pins P5.0/ADC0...P5.7/ADC7. P5 is
not affected by chip reset. P5 is a read only register. Its hardware
address is C7H. P5 is not bit addressable.
Reading Special Function Register P5 does not affect A/D
conversions. But it is recommended to use the digital input port
function of the hardware Port 5 only as an alternative to analog input
voltage conversions. Simultaneous mixed operation is discouraged
for the sake of A/D conversion result reliability and accuracy.
For further information on Port 5, refer to the “I/O facilities” section.
For further information on A/D Special Function Registers, refer to
the “Internal Data Memory” section.
P5 (C7H)
7
P5.7
6
P5.6
5
P5.5
4
P5.4
3
P5.3
2
P5.2
1
P5.1
0
P5.0
Figure 18. Digital input port register P5.
Reset
After a RESET of the microcontroller the ADCON and ADPSS
register bits are initialized to zero. Registers ADRSLn and ADRSH
are not initialized by a RESET.
Idle and Power-down Mode
The A/D Converter is active only when the microcontroller is in
normal operating mode. If the Idle or Power-down Mode is activated,
then the ADC is switched off and put into a power saving idle state –
a conversion in progress is aborted, a previously set ADSST flag is
cleared and the internal clock is halted. The conversion result
registers are not affected.
The interrupt flag ADINT will not be set by activation of Idle or
Power-down Mode. A previously set flag ADINT will not be cleared
by the hardware. (Note: ADINT cannot be cleared by hardware at
all, except for a RESET – it must be cleared by the user software.)
After a wakeup from Idle or Power-down Mode a set flag ADINT
indicates that at least one autoscan loop was finished completely
before the microcontroller was put into the respective power
reduction mode and it indicates that the stored result data may be
fetched now – if desired.
For further information on Idle and Power-down Mode, refer to the
“Power reduction modes” section.
Timing
A programmable prescaler is controlled by the bits ADPR1 and
ADPR0 in register ADCON to adapt the conversion time for different
microcontroller clock frequencies.
Table 11 shows conversion times (tconv) for one A/D conversion at
some convenient system clock frequencies (fclk) and ADC prescaler
divisors (m), which are user selectable by the bits ADCON.7/ADPR1
and ADCON.6/ADPR0.
For conversion times outside the limits for tconv the specified ADC
characteristics are not guaranteed; (prohibited conversion times are
put in brackets):
Table 11. Conversion time configuration
examples (tconv/µs)
fCLK
m
6 MHz
8 MHz
12 MHz
16 MHz
2
26
19.5
[13]
[9.75]
4
50
37.5
25
18.75
6
[74]
[55.5]
37
27.75
8
[98]
[73.5]
49
36.75
Conversion time tconv = (6 m + 1) machine cycles
A conversion time tconv consists of one sample time period (which
equals two bit conversion times), 10 bit conversion time periods and
one machine cycle to store the result.
After result storage an extra initializing time period follows to select
the next analog input channel (according to the contents of SFR
ADPSS), before the input signal is sampled.
Thus the time period between two adjacent conversions within an
autoscan loop is larger than the pure time tconv. This autoscan cycle
time is ( 7 m ) machine cycles.
At the start of an autoscan conversion the time between writing to
SFR ADCON and the first analog input signal sampling depends on
the current prescaler value (m) and the relative time offset between
this write operation and the internal (divided) ADC clock. This gives
a variation range for the A/D conversion start time of ( m / 2 )
machine cycles.
1999 Mar 02
20
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