MC68HC912BD32 Datasheet, PDF (181/292 Pages) Freescale Semiconductor, Inc – Advance Information

11-sibus
Freescale Semiconductor, Inc.
Byteflight™ Module
Functional Overview
To prepare or change a message buffer for reception the following steps
in soft reset mode are required:
• Lock the corresponding message buffer in order to appear in the
Active Receive Buffer window in the memory map.
• Wait for lock acknowledge.
• Write the matching ID to this Active Receive Buffer.
• Clear the IFLG (buffer empty) by writing a ‘1’ to it.
NOTE:
It is recommended to split clearing of the IFLG and unlocking the
message buffer into two separate instructions, i.e. clear the IFLG and
then unlock the buffer.
Once these steps are performed, the message buffer functions as an
active receive buffer and participates in the internal matching process,
which takes place every time the Byteflight™ receives a message. In this
process, all active receive buffers compare their ID value to the newly
received one. The buffer matching the received ID will be updated with
the new message at the end of reception if the buffer is not locked. The
matching buffer will be overwritten if the buffer was already full (IFLG =
1). The matching buffer will not be updated if it is still locked. The buffer
will be updated as soon as it is unlocked. If the buffer is locked for more
than one cycle and if the same ID is received twice during this period,
the buffer will be updated with the newer message as soon as it is
unlocked.
The corresponding IFLG flag (buffer full) is set every time the buffer is
updated, and if enabled a receive interrupt is generated. Erroneous
messages will be ignored and will not overwrite unlocked full buffers.
Only unique IDs must be used. ID ‘0’ should be used to deactivate a
receive buffer.
To read a receive message buffer the following steps are required:
• Lock the corresponding message buffer in order to appear in the
Active Receive Buffer window in the memory map.
• Wait for lock acknowledge.
• Read the Active Receive Buffer.
Byteflight™ Module
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MC68HC912BD32 Rev 1.0