MOD5234-100IR NetBurner Inc, MOD5234-100IR Datasheet - Page 482

• 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
21.4.5.3 Locking and Releasing Message Buffers
Besides message buffer deactivation, the lock/release/busy mechanism is designed to guarantee
data coherency during the receive process. The following examples demonstrate how the
lock/release/busy mechanism will affect FlexCAN operation.
Polling the control/status word of a receive message buffer can lock it, preventing a message from
being transferred into that buffer. If the control/status word of a receive message buffer is read, it
should then be followed by a read of the control/status word of another buffer, or by reading the
free-running timer, to ensure that the locked buffer is unlocked.
21-28
• There is a point in time until which the deactivation of a Tx MB causes it not to be
1. Reading a control/status word of a message buffer triggers a lock for that message buffer.
2. To release a locked message buffer, the CPU either locks another message buffer (by
3. If a receive frame with a matching ID is received during the time the message buffer is
4. When a locked message buffer is released, if a frame with a matching identifier exists
5. If two or more receive frames with matching IDs are received while a message buffer with
6. If the user reads the control/status word of a receive message buffer while a frame is being
Therefore, it may transmit an MB that may not have the lowest ID at the time because a
lower ID might be present that it had already scanned before the deactivation.
transmitted (end of move-out). After this point, it is transmitted but no interrupt is issued
and the CODE field is not updated.
A new received message frame that matches the message buffer cannot be written into this
message buffer while it is locked.
reading its control/status word) or globally releases any locked message buffer (by reading
the free-running timer).
locked, the receive frame will not be immediately transferred into that message buffer, but
will remain in the SMB. There is no indication when this occurs.
within the SMB, then this frame will be transferred to the matching message buffer.
a matching ID is locked, the last received frame with that ID is kept within the serial
message buffer, while all preceding ones are lost. There is no indication of lost messages
when this occurs.
transferred from a serial message buffer, the BUSY code will be indicated. The user
should wait until this code is cleared before continuing to read from the message buffer to
ensure data coherency. In this situation, the read of the control/status word will not lock
the message buffer.
MCF5235 Reference Manual, Rev. 2
Freescale Semiconductor