Freescale’s Scalable Controller Area Network (S12MSCANV3)
S12P-Family Reference Manual, Rev. 1.13
274
Freescale Semiconductor
8.3.2.18
MSCAN Identier Mask Registers (CANIDMR0–CANIDMR7)
The identier mask register species which of the corresponding bits in the identier acceptance register
are relevant for acceptance ltering. To receive standard identiers in 32 bit lter mode, it is required to
program the last three bits (AM[2:0]) in the mask registers CANIDMR1 and CANIDMR5 to “don’t care.”
To receive standard identiers in 16 bit lter mode, it is required to program the last three bits (AM[2:0])
in the mask registers CANIDMR1, CANIDMR3, CANIDMR5, and CANIDMR7 to “don’t care.”
Table 8-23. CANIDAR4–CANIDAR7 Register Field Descriptions
Field
Description
7-0
AC[7:0]
Acceptance Code Bits — AC[7:0] comprise a user-dened sequence of bits with which the corresponding bits
of the related identier register (IDRn) of the receive message buffer are compared. The result of this comparison
is then masked with the corresponding identier mask register.
Module Base + 0x0014 to Module Base + 0x0017
Access: User read/write(1)
1. Read: Anytime
Write: Anytime in initialization mode (INITRQ = 1 and INITAK = 1)
76543210
R
AM7
AM6
AM5
AM4
AM3
AM2
AM1
AM0
W
Reset
0
00000
Figure 8-22. MSCAN Identier Mask Registers (First Bank) — CANIDMR0–CANIDMR3
Table 8-24. 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 identier acceptance register must be the same as its identier 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 identier
acceptance register does not affect whether or not the message is accepted.
0 Match corresponding acceptance code register and identier bits
1 Ignore corresponding acceptance code register bit
Module Base + 0x001C to Module Base + 0x001F
Access: User read/write(1)
76543210
R
AM7
AM6
AM5
AM4
AM3
AM2
AM1
AM0
W
Reset
0
00000
Figure 8-23. MSCAN Identier Mask Registers (Second Bank) — CANIDMR4–CANIDMR7