AN2021 datasheet(21/39 Pages) STMICROELECTRONICS

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AN2021

New features

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New features

2.1

Additional XPeripherals

Some peripherals have been added to the ST10F272. They are mapped on the XBus and

are linked to additional alternate functions of some ports of the ST10F272.

The additional XPeripherals are the following:

●

A second SSC (SSC of ST10F269 becomes SSC0, while the new one is referred to as

XSSC or simply SSC1). Note that some restrictions and functional differences due to

the XBus peculiarities are present between the standard SSC, and the new XSSC.

●

A second ASC (ASC0 of ST10F269 remains ASC0, while the new one is referred to as

XASC or simply as ASC1). Note that some restrictions and functional differences due

to the XBus peculiarities are present between the standard ASC, and the new XASC.

●

An I2C interface is added (see X-I2C or simply I2C interface).

In addition to the previous XPeripherals, the ST10F272E also features a second PWM

(PWM of ST10F269 becomes PWM0, while the new one is referred to as XPWM or simply

as PWM1). Note that some restrictions and functional differences due to the XBus

peculiarities are present between the standard PWM, and the new XPWM.

2.1.1

Hardware impact

None if the additional XPeripherals are not used.

2.1.2

Software impact

None if the additional Peripherals are not used. As they are XPeripherals, they can be

enabled / disabled via the XPERCON and SYSCON registers. By default, the settings of

XPERCON and SYSCON are compatible with the ST10F269.

2.2

Programmable divider on CLKOUT

A specific register mapped on the XBus is used to choose the division factor on the

CLKOUT signal (P3.15).

XCLKOUTDIV (E902h)

XBUS

Reset value: --00h

Reserved

DIV

-R/W

Table 12.

XCLKOUTDIV register description

Bit

Function

DIV

fclkout = fCPU / (DIV + 1)

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