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P80C557E4

Single-chip 8-bit microcontroller

Philips Electronics 

Philips Semiconductors

Single-chip 8-bit microcontroller

Product specification

P83C557E4/P80C557E4/P89C557E4

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 AVref– (typical 0V) to AVref+ (typical +5V).

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:

• 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.

• 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 µs ... 50 µs

• Differential non-linearity

: DLe ±1 LSB.

• Integral non-linearity

: ILe ±2 LSB.

• Offset error

: OSe ±2LSB.

• Gain error

: Ge ±0.4 %.

• Absolute voltage error

: Ae ±3 LSB.

• Channel to channel matching : Mctc ±1LSB.

• Crosstalk between analog inputs : Ct < –60dB. @100 kHz.

• Monotonic and no missing codes.

• Separated analog (AVDD, AVSS) and digital (VDD, VSS) supply

voltages.

• Reference voltage at two special pins : AVREF– and AVREF+.

For further information on the ADC characteristics, refer to the

“DC CHARACTERISTICS” section.

6.1.1 Functional description:

Table 9. A/D Special Function Registers

SYMBOL

NAME

ADCON

A/D control register

ADPSS

Analog port scan-select register

ADRSLn

8 A/D result registers, the 8 lower bits (n: 0...7)

ADRSH

A/D result register, the 2 higher bits

P5

Digital input port (shared with analog inputs)

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.

ACCESS

read/write

read/write

read only

read only

read only

ADCON (D7H)

7

ADPR1

6

ADPR0

5

ADPOS

4

ADINT

3

ADSST

2

ADCSA

1

ADSRE

0

ADSFE

Figure 14. ADC control register.

1999 Mar 02

17

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