P80C557E4 Philips Semiconductors, P80C557E4 Datasheet - Page 17

• Manufacturer Part Number: P80C557E4
• Description: Single-chip 8-bit microcontroller
• Manufacturer: Philips Semiconductors

Philips Semiconductors
6.6 Analog/Digital Converter (ADC)
The P8xC557E4 A/D Converter is a 10-bit, successive
approximation ADC with 8 multiplexed analog input channels. It
additionally contains a high input impedance comparator, a DAC
built with 1024 series resistors and analog switches, registers and
control logic.
Input voltage range is from AV
A set of 8 buffer registers (10-bit) store the conversion results of the
proper analog input channel each.
11 Special Function Registers (SFR) perform the user software
interface to the ADC: a control SFR (ADCON), an analog port
scan-select SFR (ADPSS), 8 input channel related conversion result
SFR with the 8 lower result bits (ADRSL0...ADRSL7), one common
result SFR for the upper 2 result bits (ADRSH). An extra SFR (P5)
allows for reading digital input port data as an alternative function of
the 8 analog input pins.
In order to have a minimum of ADC service overhead in the
microcontroller program, the ADC is able to operate autonomously
within its user configurable autoscan function.
The functional diagram of the ADC is shown in Figure 15.
Feature Overview:
6.1.1 Functional description:
Table 9. A/D Special Function Registers
A/D Control Register ADCON
The Special Function Register ADCON contains control and status
bits for the A/D Converter peripheral block. The reset value of
ADCON is (00000000). Its hardware address is D7H. ADCON is not
bit addressable.
1999 Mar 02
SYMBOL
ADCON
ADPSS
ADRSLn
ADRSH
P5
10-bit resolution.
8 multiplexed analog inputs.
Programmable autoscan of the analog inputs.
Bit oriented 8-bit scan-select register to select analog inputs.
Continuous scan or one time scan configurable from 1 to 8 analog
inputs.
Single-chip 8-bit microcontroller
ADCON (D7H)
ref–
ADPR1
NAME
A/D control register
Analog port scan-select register
8 A/D result registers, the 8 lower bits (n: 0...7)
A/D result register, the 2 higher bits
Digital input port (shared with analog inputs)
(typical 0V) to AV
7
ADPR0
6
ref+
Figure 14. ADC control register.
(typical +5V).
ADPOS
5
17
ADINT
4
P83C557E4/P80C557E4/P89C557E4
For further information on the ADC characteristics, refer to the
“DC CHARACTERISTICS” section.
Start of a conversion by software or with an external signal.
Eight 10-bit buffer registers, one register for each analog input
channel.
Interrupt request after one channel scan loop.
Programmable prescaler (dividing by 2, 4, 6, 8) to adapt to
different system clock frequencies.
Conversion time for one A/D conversion: 15 s ... 50 s
Differential non-linearity
Integral non-linearity
Offset error
Gain error
Absolute voltage error
Channel to channel matching
Crosstalk between analog inputs :
Monotonic and no missing codes.
Separated analog (AV
voltages.
Reference voltage at two special pins : AV
ADSST
3
ADCSA
DD
2
, AV
SS
) and digital (V
ACCESS
read/write
read/write
read only
read only
read only
:
:
:
:
:
:
ADSRE
DLe
ILe
OSe 2LSB.
Ge
Ae
Mctc 1LSB.
Ct < –60dB. @100 kHz.
1
REF–
2 LSB.
1 LSB.
3 LSB.
0.4 %.
Product specification
DD
and AV
, V
ADSFE
SS
0
) supply
REF+
.