STR720 datasheet(219/401 Pages) STMICROELECTRONICS

219 / 401 page

STR720 - CONTROLLER AREA NETWORK (CAN)

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18.5.3

Message Interface Register Sets

There are two sets of Interface Registers, which are used to control the CPU access to the

Message RAM. The Interface Registers avoid conflict between the CPU access to the

Message RAM and CAN message reception and transmission by buffering the data to be

transferred. A complete Message Object (see Section 18.5.3.2 ) or parts of the Message

Object may be transferred between the Message RAM and the IFn Message Buffer registers

(see Section 18.5.3.1 ) in one single transfer.

The function of the two interface register sets is identical except for the Basic test mode. They

can be used the way one set of registers is used for data transfer to the Message RAM while

the other set of registers is used for the data transfer from the Message RAM, allowing both

processes to be interrupted by each other. Table 50 IF1 and IF2 Message Interface Register

Set on page 219 provides an overview of the two Interface Register sets.

Each set of Interface Registers consists of Message Buffer Registers controlled by their own

Command Registers. The Command Mask Register specifies the direction of the data transfer

and which parts of a Message Object will be transferred. The Command Request Register is

used to select a Message Object in the Message RAM as target or source for the transfer and

to start the action specified in the Command Mask Register.

Table 50. IF1 and IF2 Message Interface Register Set

Address

IF1 Register Set

Address

IF2 Register Set

CAN Base + 0x20

IF1 Command Request

CAN Base + 0x80

IF2 Command Request

CAN Base + 0x24

IF1 Command Mask

CAN Base + 0x84

IF2 Command Mask

CAN Base + 0x28

IF1 Mask 1

CAN Base + 0x88

IF2 Mask 1

CAN Base + 0x2C

IF1 Mask 2

CAN Base + 0x8C

IF2 Mask 2

CAN Base + 0x30

IF1 Arbitration 1

CAN Base + 0x90

IF2 Arbitration 1

CAN Base + 0x34

IF1 Arbitration 2

CAN Base + 0x94

IF2 Arbitration 2

CAN Base + 0x38

IF1 Message Control

CAN Base + 0x98

IF2 Message Control

CAN Base + 0x3C

IF1 Data A 1

CAN Base + 0x9C

IF2 Data A 1

CAN Base + 0x40

IF1 Data A 2

CAN Base + 0xA0

IF2 Data A 2

CAN Base + 0x44

IF1 Data B 1

CAN Base + 0xA4

IF2 Data B 1

CAN Base + 0x48

IF1 Data B 2

CAN Base + 0xA8

IF2 Data B 2

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