AN2021 datasheet(18/39 Pages) STMICROELECTRONICS

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Modified features

AN2021

18/39

1.7.1

Hardware impact

None.

1.7.2

Software impact

None if the software is not writing to PICON bit 5 (P6LIN).

1.8

Ports output control

In the ST10F269, the port output control registers POCONx are used to select the output

driver characteristics of a port. In this way, the output drivers can be adapted to the

application’s requirements, and eventually, the EMI behavior of the device can be improved.

Two characteristics may be selected:

●

Edge characteristic defines the rise/fall time for the respective outputs, that is, the

transition time. Slow edge reduces the peak currents that are sunk/sourced when

changing the voltage level of an external capacitive load.

●

Driver characteristic defines either the general driving capability of the respective

drivers, or if the driver strength is reduced after the target output level has been

reached or not. Reducing the driver strength increases the output’s internal resistance,

which attenuates noise that is imported via the output line.

This feature is not available on the ST10F272.

1.8.1

Hardware impact

Some modifications might be needed depending on the usage of this functionality.

1.8.2

Software impact

Parts related to the initialization of the POCONx registers should be suppressed.

1.9

PLL and main on-chip oscillator

Compared to the ST10F269, several modifications have been introduced:

●

PLL multiplication factors have been adapted in order to match the new frequency

range.

●

On-chip main oscillator input frequency range has been reshaped, reducing it to 4 to

8 MHz: This allows the power consumption to be reduced when the Real Time Clock is

Table 10.

PICON register description

Bit

Function

Reset value

PxLIN

Port x Low Byte Input Level Selection

0: Pins Px.7..0 switch on standard TTL input levels

1: Pins Px.7..0 switch on CMOS input levels

PxHIN

Port x High Byte Input Level Selection

0: Pins Px.15..8 switch on standard TTL input levels

1: Pins Px.15..8 switch on CMOS input levels

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