MC9S12XD256MAL Datasheet, PDF (445/1348 Pages) Freescale Semiconductor, Inc – Freescale’s Scalable Controller Area Network

Chapter 10 Freescale’s Scalable Controller Area Network (S12MSCANV3)
Table 10-23. CANIDMR4–CANIDMR7 Register Field Descriptions
Field
Description
7:0
AM[7:0]
Acceptance Mask Bits — If a particular bit in this register is cleared, this indicates that the corresponding bit in
the identifier acceptance register must be the same as its identifier bit before a match is detected. The message
is accepted if all such bits match. If a bit is set, it indicates that the state of the corresponding bit in the identifier
acceptance register does not affect whether or not the message is accepted.
0 Match corresponding acceptance code register and identifier bits
1 Ignore corresponding acceptance code register bit
10.3.3 Programmer’s Model of Message Storage
The following section details the organization of the receive and transmit message buffers and the
associated control registers.
To simplify the programmer interface, the receive and transmit message buffers have the same outline.
Each message buffer allocates 16 bytes in the memory map containing a 13 byte data structure.
An additional transmit buffer priority register (TBPR) is defined for the transmit buffers. Within the last
two bytes of this memory map, the MSCAN stores a special 16-bit time stamp, which is sampled from an
internal timer after successful transmission or reception of a message. This feature is only available for
transmit and receiver buffers, if the TIME bit is set (see Section 10.3.2.1, “MSCAN Control Register 0
(CANCTL0)”).
The time stamp register is written by the MSCAN. The CPU can only read these registers.
Table 10-24. Message Buffer Organization
Offset
Address
0x00X0
0x00X1
0x00X2
0x00X3
0x00X4
0x00X5
0x00X6
0x00X7
0x00X8
0x00X9
0x00XA
0x00XB
0x00XC
0x00XD
0x00XE
0x00XF
Register
Identifier Register 0
Identifier Register 1
Identifier Register 2
Identifier Register 3
Data Segment Register 0
Data Segment Register 1
Data Segment Register 2
Data Segment Register 3
Data Segment Register 4
Data Segment Register 5
Data Segment Register 6
Data Segment Register 7
Data Length Register
Transmit Buffer Priority Register¹
Time Stamp Register (High Byte)²
Time Stamp Register (Low Byte)³
Access
MC9S12XDP512 Data Sheet, Rev. 2.21
Freescale Semiconductor
445