AN1313 - APPLICATION NOTE

12/16

5.1.1.1 - Hardware Impacts

None.

5.1.1.2 - Software Impacts

The value has to be changed from its default reset one to match XRAM size compatibility. Refer to XRAM

section for more details.

5.1.2 - POCONx Registers

These are new registers of the ST10F269.

The port output control registers POCONx allow to select the port output driver characteristics of a port.

The aim of these selections is to adapt the output drivers to the application’s requirements, and to

improve the EMI behavior of the device. Two characteristics may be selected:

– Edge characteristic defines the rise/fall time for the respective output, i.e. the transition time. Slow

edge reduce the peak currents that are sunk/sourced when changing the voltage level of an external

capacitive load. For a bus interface or pins that are changing at frequency higher than 1MHz, however,

fast edges may still be required.

– Driver characteristic defines either the general driving capability of the respective driver, 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.

For driving LEDs or power transistors, however, a stable high output current may still be required.

POCONx

ESFR

Reset Value: 0000h

The new registers are the following:

– POCON0L, POCON0H, POCON1L, POCON1H, POCON2, POCON3, POCON4, POCON5, POCON6,

POCON7 and POCON8 dealing with the respective ports,

– POCON20 dealing with the dedicated pins ALE, RD and WR.

5.1.2.1 - Hardware Impacts

ST10F168 and ST10F269 ports don’t have the same behavior in their default reset configuration. The

ST10F269 default reset values select the “Fast Edge Mode” and the “High Current Mode”, while the

ST10F168 is designed for “Fast Edge Mode” and “Dynamic Current Mode”.

15

14

13

12

11

10

9876543210

PNzDC

PNzEC

PNyDC

PNyEC

PNxEC

PNxEC

PNwEC

PNwEC

RW

RW

RW

RW

RW

RW

RW

RW

Table 4 : POCONx Registers Bits

Bit

Function

Reset value

PNxEC

00

01

10

11

Port Nibble x Edge Characteristic (rise/fall time)

Fast edge mode, rise/fall times depend on the driver’s dimensioning.

Slow edge mode, rise/fall times ~60 ns

Reserved

Reserved

00

PNxDC

00

01

10

11

Port Nibble x Driver Characteristic (output current)

High Current mode:

Driver always operates with maximum strength.

Dynamic Current mode:

Driver strength is reduced after the target level has been reached.

Low Current mode:

Driver always operates with reduced strength.

Reserved

00