AN2555 - Application note

Modified features

11/33

duration of self-calibration depends on the CPU clock: It may take up to 40.629 ± 1 clock pulses. The

user must poll this bit to know when self-calibration is complete in order to initialize the ADC module.

This self-calibration is seen by the ST10F276Z5 as a conversion and thus bit ADCIR is set. The software

must perform a dummy read of the ADDAT register and clear the ADCIR and ADCEIR flags before

configuring the ADC module and starting the first conversion.

New bit ADOFF, bit 6 of ADCON register

ADCON (FFA0h / A0h)

SFR

Reset Value: 0000h

The bit 6 of the ADCON register, reserved in previous ST10 devices, is now used to enable or disable the

ADC. By default this bit is cleared and the ST10F276Z5 is compatible with the ST10F269Zx. Therefore

there is no impact on the software, provided that the software does not write to this bit.

Additional analog channels on Port1

A new multiplexer selects one out of up to 16+8 analog input channels (alternate functions of Port 5 and

Port1). The selection of Port1 or Port5 as input of the ADC is made via ADCMUX, bit 0 of XMISC register.

By default the multiplexer selects Port5, so there is no impact on the software as compared to an

ST10F269Zx implementation.

Note that XMISCEN, bit 10 of the XPERCON register, must be set to have access to the XMISC register.

XMISC (EB46h)

XREG

Reset Value: --00h

15

14

13

12

11

10

9

8

7

6

543

210

ADCTC

ADSTC

ADCTC ADCIN ADWR ADBSY ADST ADOFF

ADM

ADCH

RW

RW

RW

RW

RW

R

RW

RW

RW

RW

Bit

Function

Comment

ADOFF

ADC Disable

‘0’: Analog circuitry of A/D converter is on

‘1’: Analog circuitry of A/D converter is turned off (no

consumption)

New bit only for the

ST10F276Z5.

Reserved for the

ST10F269Zx.

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

--

--

--

--

--

--

VREGOFF CANCK2 CANPAR ADCMUX

RW

RW

RW

RW

Bit

Function

ADCMUX

‘0’ default configuration, analog inputs on port P5.y can be converted

‘1’ analog inputs on port P1.z can be converted, only 8 channel can be managed