K60P100M100SF2RM Datasheet, PDF (1339/1809 Pages) Freescale Semiconductor, Inc – K60 Sub-Family Reference Manual

Field
23–19
TASD
Chapter 48 CAN (FlexCAN)
CANx_CTRL2 field descriptions (continued)
Description
The number of remaining Mailboxes available will be:
(SETUP_MB - 8) - (RFFN x 2)
If the Number of Rx FIFO Filters programmed through RFFN exceeds the SETUP_MB value
(memory space available) the exceeding ones will not be functional.
RFFN[3:
0]
Number
of Rx
FIFO
filters
Message
Buffers
occupied by Rx
FIFO and ID
Filter Table
Remaining
Available
Mailboxes¹
0x0
8
MB 0-7
MB 8-63
0x1
16
MB 0-9
MB 10-63
0x2
24
MB 0-11
MB 12-63
0x3
32
MB 0-13
MB 14-63
0x4
40
MB 0-15
MB 16-63
0x5
48
MB 0-17
MB 18-63
0x6
56
MB 0-19
MB 20-63
0x7
64
MB 0-21
MB 22-63
0x8
72
MB 0-23
MB 24-63
0x9
80
MB 0-25
MB 26-63
0xA
88
MB 0-27
MB 28-63
0xB
96
MB 0-29
MB 30-63
0xC
104
MB 0-31
MB 32-63
0xD
112
MB 0-33
MB 34-63
0xE
120
MB 0-35
MB 36-63
0xF
128
MB 0-37
MB 38-63
Rx FIFO ID Filter
Table Elements
Affected by Rx
Individual Masks²
Rx FIFO ID Filter
Table Elements
Affected by Rx
FIFO Global Mask²
Elements 0-7
Elements 0-9
Elements 0-11
Elements 0-13
Elements 0-15
Elements 0-17
Elements 0-19
Elements 0-21
Elements 0-23
Elements 0-25
Elements 0-27
Elements 0-29
Elements 0-31
Elements 0-31
Elements 0-31
Elements 0-31
none
Elements 10-15
Elements 12-23
Elements 14-31
Elements 16-39
Elements 18-47
Elements 20-55
Elements 22-63
Elements 24-71
Elements 26-79
Elements 28-87
Elements 30-95
Elements 32-103
Elements 32-111
Elements 32-119
Elements 32-127
1. The number of the last remaining available mailboxes is defined by the least value between the
parameter NUMBER_OF_MB minus 1 and the MCR[MAXMB] field.
2. If Rx Individual Mask Registers are not enabled then all Rx FIFO filters are affected by the Rx FIFO
Global Mask.
Tx Arbitration Start Delay
This 5-bit field indicates how many CAN bits the Tx arbitration process start point can be delayed from the
first bit of CRC field on CAN bus. This field can only be written in Freeze mode as it is blocked by
hardware in other modes.
This field is useful to optimize the transmit performance based on factors such as: peripheral/serial clock
ratio, CAN bit timing and number of MBs. The duration of an arbitration process, in terms of CAN bits, is
directly proportional to the number of available MBs and CAN baud rate and inversely proportional to the
peripheral clock frequency.
The optimal arbitration timing is that in which the last MB is scanned right before the first bit of the
Intermission field of a CAN frame. Therefore, if there are few MBs and the system/serial clock ratio is high
and the CAN baud rate is low then the arbitration can be delayed and vice-versa.
Table continues on the next page...
K60 Sub-Family Reference Manual, Rev. 6, Nov 2011
Freescale Semiconductor, Inc.
1339