Modified features

AN2556

12/35

1.4.3

Software impacts

Self-calibration and ADC initialization routine

An automatic self-calibration adjusts the ADC module to process parameter variations at

each reset event. After reset, the busy flag (read-only) ADBSY is set because the self-

calibration is ongoing. The duration of self-calibration depends on the CPU clock: It takes up

to 40.629 ± 1 clock pulse. The user should poll this bit to know when the self-calibration is

done and then initialize the ADC module.

Such self-calibration is seen in the ST10F273Z4 as a conversion and thus the ADCIR bit is

set. The software should perform a dummy read of the ADDAT register and clear the ADCIR

and ADCEIR flag before configuring the ADC module and starting the first conversion.

Bit 6 of the ADCON register was reserved in previous ST10 devices. It now has the function

of enabling or disabling the ADC. By default this bit is cleared and the ST10F273Z4 is

compatible with ST10F269Zx. Therefore, there is no impact on the software, provided it is

not written to this bit.

Reference supply current

µA

Running mode

-

500

-

500

Power-down mode

-

1

-

1

Differential nonlinearity

DNL

-0.5

+0.5

1

1

LSB

Integral nonlinearity

INL

-1.5

+1.5

-1.5

1.5

LSB

Offset error

OFS

-1.0

+1.0

-1.5

1.5

LSB

1.

pin on the ST10F273Z4 with regard to the ST10F269Zx, avoid using a resistor (for example, because of an

RC filter). This creates an offset in the reference.

Table 6.

ADC differences (continued)

Parameter

Symbol

Limit values for

ST10F269Zx

Limit values for

ST10F273Z4

Unit

Min

Max

Min

Max

ADCON (FFA0h / A0h)

SFR

Reset value: 0000h

15

14

13

12

11

10

987

65432

10

ADCTC

ADSTC

ADC

RQ

ADC

IN

AD

WR

AD

BSY

AD

ST

AD

OFF

ADM

ADCH

RW

RW

RW

RW

RW

RO

RW

RW

RW

RW

Table 7.

ADCON register: ADOFF bit

Bit

Function

CommentS

ADOFF

ADC disable

0: Analog circuitry of A/D converter is turned on.

1: Analog circuitry of A/D converter is turned off.

New bit valid only for the ST10F273Z4.

Reserved for the ST10F269Zx.