HCS08 datasheet(23/198 Pages) NXP

23 / 198 page

Chapter 2 External Signal Description

MC9S08QD4 Series MCU Data Sheet, Rev. 6

Freescale Semiconductor

2.2.5.2

Output Slew Rate Control

Slew rate control can be enabled for each port pin by setting the corresponding bit in one of the slew rate

control registers (PTxSEn). When enabled, slew control limits the rate at which an output can transition in

order to reduce EMC emissions. Slew rate control has no effect on pins that are configured as inputs.

2.2.5.3

Output Drive Strength Select

An output pin can be selected to have high output drive strength by setting the corresponding bit in one of

the drive strength select registers (PTxDSn). When high drive is selected, a pin is capable of sourcing and

sinking greater current. Even though every I/O pin can be selected as high drive, the user must ensure that

the total current source and sink limits for the chip are not exceeded. Drive strength selection is intended

to affect the DC behavior of I/O pins. However, the AC behavior is also affected. High drive allows a pin

to drive a greater load with the same switching speed as a low drive enabled pin into a smaller load.

Because of this, the EMC emissions may be affected by enabling pins as high drive.

Table 2-1. Pin Sharing Priority

Lowest <- Pin Function Priority -> Highest

Reference1

1 See the module section listed for information on modules that share these pins.

Port Pins

Alternative

Function

Alternative

Function

Alternative

Function

PTA0

PTA1

PTA2

PTA3

PTA4

PTA52

2 Pin does not contain a clamp diode to V

DD and must not be driven above VDD. The voltage measured on this

pin when internal pullup is enabled may be as low as VDD – 0.7 V. The internal gates connected to this pin are

pulled to VDD.

KBI1P0

KBI1P1

KBI1P2

KBI1P3

TPM2CH0O

TPM2CH0I

TPM1CH0

TPM1CH1

TCLK1

TCLK2

BKGD/MS

IRQ

ADC1P03

ADC1P13

ADC1P23

ADC1P33

RESET

3 If both of these analog modules are enabled both will have access to the pin.

KBI1, ADC1, and TPM1 Chapters

KBI1, ADC1, and TPM2 Chapters

TPM2 Chapters

IRQ4, and TPM2 Chapters

4 See Section 5.8, “Reset, Interrupt, and System Control Registers and Control Bits,” for information on

configuring the IRQ module.

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