AN2021 datasheet(15/39 Pages) STMICROELECTRONICS

15 / 39 page

AN2021

Modified features

15/39

Additional channels on Port1 - only for the ST10F272E

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 the input of the ADC is made via bit

ADCMUX, bit 0 of the XMISC register. By default the multiplexer selects Port5, so there is no

impact on the software as compared to an ST10F269 implementation. Note that XMISCEN,

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

Note:

In the ST10F272B, the location of the ADCMUX bit is reserved and should not be written to,

or only to value ‘0’.

1.5

Real time clock

The RTC module can be clocked by two different sources: the main oscillator (pins XTAL1

and XTAL2) or the 32 kHz oscillator (pins XTAL3 and XTAL4). The selection of the clocking

can be made via an additional bit in the RTCCON register.

1.5.1

Hardware impact

Check the usage of pins XTAL3 and XTAL4 (pins 143 and 144, respectively).

1.5.2

Software impact

The address range of the RTC registers has been modified from 00’EC00h - 00’ECFFh on

the ST10F269, to 00’ED00h - 00’EDFFh on the ST10F272. This relocation has no impact if

the software uses register names defined by the toolchain and if the CPU selection is

changed to ST10F272. If the software was directly using the address of the RTC register, it

must be modified according to the new mapping.

XMISC (EB46h)

XREG

Reset value: --00h

Reserved

VREG

OFF

CAN

CK2

CAN

PAR

ADC

MUX

R/W

Table 8.

XMISC register description

Bit

Function

ADCMUX

ADC Multiplexer

0: Default configuration, analog inputs on port P5.y can be converted

1: Analog inputs on port P1.z can be converted, only 8 channels can be

managed

ST10F269: RTCCON (F1C4h / E2h)

ESFR

Reset value: --00h

Reserved

RTC

OFF

Reserved

RTC

AEN

RTC

AIR

RTC

SEN

RTC

SIR

R/W

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