Migrating from Atmel C51/CAN: T89C51CC01,

AT89C51CC03 To Atmel AVR/CAN: AT90CAN128,

AT90CAN64, AT90CAN32

Introduction

This application note is a guide, on the CAN controller, to help current T89C51CC01,

AT89C51CC03 users convert existing designs to AT90CAN128, AT90CAN64,

AT90CAN32. The CAN controller used in T89C51CC01/AT89C51CC03 and the CAN

controller used in AT90CAN128 are almost identical. this application note presents

their differences and helps users take advantage of additional features.

Check the datasheets of these products for detailed information.

Same CAN controller

The CAN controller implemented into AT89C51CC01, AT89C51CC03, AT90CAN128,

AT90CAN64, AT90CAN32 offers V2.0B Active. This full-CAN controller provides the

whole hardware for convenient acceptance filtering and message management. For

each message to be transmitted or received this module contains one so called mes-

sage object in which all information regarding the message (e.g. identifier, data bytes

etc.) is stored.

During the initialization of the peripheral, the application defines which messages are

to be sent and which are to be received. When the CAN controller receives a mes-

sage whose identifier matches the identifiers of the programmed message objects, the

message is stored and an interrupt occurs.

Another advantage is that incoming remote frames can be answered automatically by

the full-CAN controller with the corresponding data frame. In this way, CPU load is

strongly reduced compared to a basic-CAN solution. Using full-CAN controller, high

baudrates and high bus loads with many messages can be handled.

The CNHPMOB and BOFF registers have been added to the following products

AT90CAN128, AT90CAN64, AT90CAN32

BOFF (Bus OFF Mode)

BOFF gives the information of the state of the CAN channel. Only entering in bus Off

mode generates the BOFFIT interrupt.

CANHPMOB (CAN Highest Priority MOB Register)

This register offer the possibility to quickly manage the MOB having the highest prior-

ity in CANSIT registers.

AVR/CAN controller = C51/CAN controller + BOFFIT + CANHPMOB

7528A–CAN–06/05

CAN, 80C51,

AVR,

Microcontroller

Application Note