MOD5234-100IR NetBurner Inc, MOD5234-100IR Datasheet - Page 480

• Manufacturer Part Number: MOD5234-100IR
• Description: MOD5234 10/100 ETHERNET MODULE
• Manufacturer: NetBurner Inc
• Type: Controllers & Processorsr

Specifications of MOD5234-100IR

• Interface: I²C, SPI, UART
• Voltage - Supply: 2.5V
• Mounting Type: Surface Mount
• Package / Case: Module
• Product: Modules
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Data Format: -
• Baud Rates: -
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant
• Other names: Q4483564

FlexCAN
newly received frame matching the ID of that MB may be lost. In summary, never do polling by
directly reading the C/S word of the MBs. Instead, read the IFLAGn register.
Note that the received identifier field is always stored in the matching MB, thus the contents of the
ID field in an MB may change if the match was due to masking.
21.4.3.1 Self-Received Frames
Self-received frames are frames that are sent by the FlexCAN and received by itself. The FlexCAN
sends a frame externally through the physical layer onto the CAN bus, and if the ID of the frame
matches the ID of the FlexCAN MB, then the frame will be received by the FlexCAN. Such a
frame is a self-received frame. Note that FlexCAN does not receive frames transmitted by itself if
another device on the CAN bus has an ID that matches the FlexCAN Rx MB ID.
21.4.4 Matching Process
The matching process is an algorithm that scans the entire MB memory looking for Rx MBs
programmed with the same ID as the one received from the CAN bus. Only MBs programmed to
receive will participate in the matching process for received frames.
While the ID, DLC and data fields are retrieved from the CAN bus, they are stored temporarily in
the Serial Message Buffer
(Section 21.4.5.1, “Serial Message Buffers
(SMBs)). The matching
process takes place during the CRC field. If a matching ID is found in one of the MBs, the contents
of the SMB will be transferred to the matched MB during the sixth bit of the end-of-frame field of
the CAN protocol. This operation is called “move-in”. If any protocol error (CRC, ACK, etc.) is
detected, than the move-in operation does not happen.
An MB with a matching ID is “free to receive” a new frame if the MB is not locked (see
Section 21.4.5.3, “Locking and Releasing Message
Buffers”) and the CODE field is either
EMPTY or else it is FULL or OVERRUN but the CPU has already serviced the MB (read the C/S
word and then unlocked the MB).
If the first MB with a matching ID is not “free to receive” the new frame, then the matching
algorithm will overwrite the matching MB (unless it is locked) and set the CODE field to
OVERRUN (refer to
Table
21-13). If the last matching MB is locked, then the new message
remains in the SMB, waiting for the MB to be unlocked (see
Section 21.4.5.3, “Locking and
Releasing Message
Buffers”).
Matching to a range of IDs is possible by using ID acceptance masks (RXGMASKn,
RX14MASKn, and RX15MASKn). During the matching algorithm, if a mask bit is asserted, then
the corresponding ID bit is compared. If the mask bit is negated, the corresponding ID bit is “don’t
care”.
MCF5235 Reference Manual, Rev. 2
21-26
Freescale Semiconductor