Functional Description

To configure a pin for input capture:

1.Clear the pin’s IOS bit in GPTIOS.

2.Clear the pin’s DDR bit in PORTTnDDR.

3.Write to GPTCTL2 to select the input edge to detect.

PORTTnDDR does not affect the data direction of an output compare pin. The output compare function overrides the data direction register but does not affect the state of the data direction register.

To configure a pin for output compare:

1.Set the pin’s IOS bit in GPTIOS.

2.Write the output compare value to GPTCn.

3.Clear the pin’s DDR bit in PORTTnDDR.

4.Write to the OMn/OLn bits in GPTCTL1 to select the output action.

Table 20-23shows how various timer settings affect pin functionality.

Table 20-23. GPT Settings and Pin Functions

GPTEN

DDR 1

GPTIOS

EDGx

OMx/

OC3Mx 3

Pin

Pin

Pin

 

Data

Driven

Comments

 

 

 

[B:A]

OLx 2

 

Dir.

by

Function

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

0

0

X 4

X

X

X

In

Ext.

Digital input

GPT disabled by GPTEN = 0

0

1

X

X

X

X

Out

Data reg.

Digital output

GPT disabled by GPTEN = 0

 

 

 

 

 

 

 

 

 

 

1

0

0 (IC)

0 (IC

X

0

In

Ext.

Digital input

Input capture disabled by EDGn

 

 

 

disable

 

 

 

 

 

setting

 

 

 

d)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1

1

0

0

X

0

Out

Data reg.

Digital output

Input capture disabled by EDGn

 

 

 

 

 

 

 

 

 

setting

 

 

 

 

 

 

 

 

 

 

1

0

0

<> 0

X

0

In

Ext.

IC and

Normal settings for input capture

 

 

 

 

 

 

 

 

digital input

 

 

 

 

 

 

 

 

 

 

 

1

1

0

<> 0

X

0

Out

Data reg.

Digital output

Input capture of data driven to output

 

 

 

 

 

 

 

 

 

pin by CPU

 

 

 

 

 

 

 

 

 

 

1

0

0

<> 0

X

1

In

Ext.

IC and

OC3M setting has no effect because

 

 

 

 

 

 

 

 

digital input

IOS = 0

 

 

 

 

 

 

 

 

 

 

1

1

0

<> 0

X

1

Out

Data reg.

Digital output

OC3M setting has no effect because

 

 

 

 

 

 

 

 

 

IOS = 0; input capture of data driven

 

 

 

 

 

 

 

 

 

to output pin by CPU

 

 

 

 

 

 

 

 

 

 

1

0

1 (OC)

X(3)

0 5

0

In

Ext.

Digital input

Output compare takes place but

 

 

 

 

 

 

 

 

 

does not affect the pin because of

 

 

 

 

 

 

 

 

 

the OMn/OLn setting

 

 

 

 

 

 

 

 

 

 

1

1

1

X

0

0

Out

Data reg.

Digital output

Output compare takes place but

 

 

 

 

 

 

 

 

 

does not affect the pin because of

 

 

 

 

 

 

 

 

 

the OMn/OLn setting

 

 

 

 

 

 

 

 

 

 

1

0

1

X

<> 0

0

Out

OC action

Output compare

Pin readable only if DDR = 0(5)

20-20

MCF5282 User’s Manual

MOTOROLA

Page 442
Image 442
Motorola MCF5282, MCF5281 user manual GPT Settings and Pin Functions, EDGx OMx OC3Mx Pin Data Driven Comments, Dir Function