PXS20RM Datasheet, PDF (615/1368 Pages) Freescale Semiconductor, Inc – PXS20 Microcontroller

FlexCAN Module
Upon reset this bit is negated, allowing legacy software to work without modification. This bit must
be written in Freeze mode only.
1 = Individual Rx masking and queue feature are enabled.
0 = Individual Rx masking and queue feature are disabled.
LPRIO_EN— Local Priority Enable
This bit is provided for backwards compatibility reasons. It controls whether the local priority feature
is enabled or not. It is used to extend the ID used during the arbitration process. With this extended ID
concept, the arbitration process is done based on the full 32-bit word, but the actual transmitted ID still
has 11-bit for standard frames and 29-bit for extended frames. This bit must be written in Freeze mode
only.
1 = Local Priority enabled
0 = Local Priority disabled
AEN— Abort Enable
This bit is supplied for backwards compatibility reasons. When asserted, it enables the Tx abort
feature. This feature guarantees a safe procedure for aborting a pending transmission, so that no frame
is sent in the CAN bus without notification. This bit must be written in Freeze mode only.
1 = Abort enabled
0 = Abort disabled
IDAM — ID Acceptance Mode
This 2-bit field identifies the format of the elements of the Rx FIFO filter table, as shown in Table 24-6.
Note that all elements of the table are configured at the same time by this field (they are all the same
format). See Section 24.3.3, Rx FIFO Structure. This bit must be written in Freeze mode only.
Table 24-6. IDAM Coding
IDAM
0b00
0b01
0b10
0b11
Format
A
B
C
D
Explanation
One full ID (standard or extended) per filter element.
Two full standard IDs or two partial 14-bit extended IDs per filter element.
Four partial 8-bit IDs (standard or extended) per filter element.
All frames rejected.
MAXMB — Maximum Number of Message Buffers
This 6-bit field defines the maximum number of message buffers that will take part in the matching
and arbitration processes. The reset value (0x0F) is equivalent to 16 MB configuration. This field must
be changed only while the module is in Freeze Mode.
Maximum MBs in use = MAXMB + 1.
NOTE
MAXMB must be programmed with a value smaller or equal to the number
of available Message Buffers, otherwise FlexCAN can transmit and receive
wrong messages.
Freescale Semiconductor
PXS20 Microcontroller Reference Manual, Rev. 1
24-15