Functional Description
When 32 bytes of a message longer than that are stored in the RFIFO, the CPU is prompted
to read out the data by an RPF interrupt. The CPU must handle this interrupt before more than
32 additional bytes are received, which would cause a "data overflow" (figure 59).This
corresponds to a maximum CPU reaction time of 16 ms (data rate 16 kbit/s).
After a remaining block of less than or equal to 16 bytes has been stored, it is possible to store
the first 16 bytes of a new message (see figure 59).
The internal memory is now full. The arrival of additional bytes will result in "data overflow"
(RSTA:RDO) and a third new message in "frame overflow" (EXIR:RFO).
The generated interrupts are inserted together with all additional information into a queue to
be individually passed to the CPU.
After an RPF or RME interrupt has been processed, i.e. the received data has been read from
the RFIFO, this must be explicitly acknowledged by the CPU issuing an RMC (Receive
Message Complete) command.
The ISAC-S can then release the associated FIFO pool for new data. If there is an additional
interrupt in the queue it will be generated after the RMC acknowledgement.
RFIFO
the Queue
Interrupts in
RFIFO
Interrupts in
the Queue
0
0
Long
Message 1
(
Long
Message
_
<
46 bytes)
31
0
31
0
RPF
RPF
15
16
RME
Message 2
_
<
(
32 bytes)
31
31
RPF
RME
ITS01501
Figure 59
Contents of the RFIFO (long messages)
Semiconductor Group
113
INFINEON [ Infineon ]
