Freescale Semiconductor DEMO9S08DZ60 Demo Board DEMO9S08DZ60 DEMO9S08DZ60 数据表
产品代码
DEMO9S08DZ60
Chapter 12 Freescale’s Controller Area Network (S08MSCANV1)
MC9S08DZ60 Series Data Sheet, Rev. 4
Freescale Semiconductor
241
Read: Anytime
Write: Anytime in initialization mode (INITRQ = 1 and INITAK = 1)
Write: Anytime in initialization mode (INITRQ = 1 and INITAK = 1)
12.4
Programmer’s Model of Message Storage
The following section details the organization of the receive and transmit message buffers and the
associated control registers.
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.
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
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
The time stamp register is written by the MSCAN. The CPU can only read these registers.
Table 12-22. CANIDMR0–CANIDMR3 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 (don’t care)
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 (don’t care)
7
6
5
4
3
2
1
0
R
AM7
AM6
AM5
AM4
AM3
AM2
AM1
AM0
W
Reset
0
0
0
0
0
0
0
0
Figure 12-22. MSCAN Identifier Mask Registers (Second Bank) — CANIDMR4–CANIDMR7
Table 12-23. 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 (don’t care)
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 (don’t care)