at89c51cc02ua-tdsum ATMEL Corporation, at89c51cc02ua-tdsum Datasheet - Page 80

• Manufacturer Part Number: at89c51cc02ua-tdsum
• Description: At89c51cc02, T89c51cc02 Enhanced 8-bit Microcontroller With Can Controller And Flash
• Manufacturer: ATMEL Corporation

Working on Message Objects
CAN Controller
Management
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AT/T89C51CC02
The Page message object register (CANPAGE) is used to select one of the 4 message
objects. Then, message object Control (CANCONCH) and message object Status
(CANSTCH) are available for this selected message object number in the corresponding
SFRs. A single register (CANMSG) is used for the message. The mailbox pointer is
managed by the Page message object register with an auto-incrementation at the end of
each access. The range of this counter is 8.
Note that the maibox is a pure RAM, dedicated to one message object, without overlap.
In most cases, it is not necessary to transfer the received message into the standard
memory. The message to be transmitted can be built directly in the maibox. Most calcu-
lations or tests can be executed in the mailbox area which provide quicker access.
In order to enable the CAN Controller correctly the following registers have to be
initialized:
•
•
•
During operation, the CAN Enable message object registers (CANEN) gives a fast over-
view of the message objects availability.
The CAN messages can be handled by interrupt or polling modes.
A message object can be configured as follows:
•
•
•
•
This configuration is made in the CONCH field of the CANCONCH register (See
Table 54).
When a message object is configured, the corresponding ENCH bit of CANEN register
is set.
Table 54. Configuration for CONCH1:2
When a Transmitter or Receiver action of a message object is completed, the corre-
sponding ENCH bit of the CANEN register is cleared. In order to re-enable the message
object, it is necessary to re-write the configuration in CANCONCH register.
Non-consecutive message objects can be used for all three types of message objects
(Transmitter, Receiver and Receiver buffer).
CONCH 1
General Control (CANGCON),
bit Timing (CANBT 1, 2 & 3),
And for each page of 15 message objects:
–
–
Transmit message object
Receive message object
Receive buffer message object
Disable
0
0
1
1
Message object Control (CANCONCH),
Message object Status (CANSTCH).
CONCH 2
0
1
0
1
Type of Message Object
Disable
Transmitter
Receiver
Receiver buffer
4126L–CAN–01/08