XC164-16 Datasheet, PDF (315/417 Pages) Infineon Technologies AG – 16-Bit Single-Chip Microcontroller with C166SV2 Core Volume 2 (of 2): Peripheral Units

XC164-16 Derivatives
Peripheral Units (Vol. 2 of 2)
TwinCAN Module
21.1.4 Message Handling Unit
A message object is the basic information unit exchanged between the CPU and the
CAN controller. 32 message objects are provided by the internal CAN memory. Each of
these objects has an identifier, its own set of control and status bits and a separate data
area. Each message object covers 32 bytes of internal memory subdivided into control
registers and data storage as illustrated in Figure 21-9.
Module Offset + 300_H + n*20_H
Message Object n
Data
+00_H
Arbitration (Identifier)
Acceptance Mask
Message Control
Message Configuration
FIFO/Gateway Control
+08_H
+0C_H
+10_H
+14_H
+18_H
MCA05479
Figure 21-9 Structure of a Message Object
In normal operation mode, each message object is associated with one CAN node. Only
in shared gateway mode, a message object can be accessed by both CAN nodes
(according to the corresponding bitfield NODE).
In order to be taken into account by the respective CAN node control logic, the message
object must be declared valid in its associated message control register (bit MSGVAL).
When a message object is initialized by the CPU, bitfield MSGVAL in message control
register MSGCTRn should be reset, inhibiting a read or write access of the CAN node
controller to the associated register and data buffer storage. Afterwards, the message
identifier and operation mode (transmit, receive) must be defined. If a successful
transmission and/or reception of a message object should be followed by the execution
of an interrupt service routine, the respective bitfields TXIE and RXIE have to be set and
the interrupt pending indicator (bitfield INTPND) should be reset.
If the automatic response of an incoming remote frame with matching identifier is not
requested, the respective transmission message object should be configured with
CPUUPD = ‘10’.
As soon as bitfield MSGVAL is set to ‘10’, the respective message object is operable and
taken into account by the associated CAN node controller.
User’s Manual
TwinCAN_X41, V2.1
21-15
V2.1, 2004-03