upd70f3402 Renesas Electronics Corporation., upd70f3402 Datasheet - Page 634

• Manufacturer Part Number: upd70f3402
• Description: 32-/16-bit Single-chip Microcontroller With Can Interface
• Manufacturer: Renesas Electronics Corporation.

16.9.4 Multi buffer receive block function
The multi buffer receive block (MBRB) function is used to store a block of data in two or more message
buffers sequentially with no CPU interaction, by setting the same ID to two or more message buffers
with the same message buffer type.
Suppose, for example, the same message buffer type is set to 10 message buffers, message buffers 10
to 19, and the same ID is set to each message buffer. If the first message whose ID matches an ID of
the message buffers is received, it is stored in message buffer 10. At this point, the DN bit of message
buffer 10 is set, prohibiting overwriting the message buffer when subsequent messages are received.
When the next message with a matching ID is received, it is received and stored in message buffer 11.
Each time a message with a matching ID is received, it is sequentially (in the ascending order) stored in
message buffers 12, 13, and so on. Even when a data block consisting of multiple messages is
received, the messages can be stored and received without overwriting the previously received match-
ing-ID data.
Whether a data block has been received and stored can be checked by setting the IE bit of the CnMC-
TRLm register of each message buffer. For example, if a data block consists of k messages, k message
buffers are initialized for reception of the data block. The IE bit in message buffers 0 to (k-2) is cleared
to 0 (interrupts disabled), and the IE bit in message buffer k-1 is set to 1 (interrupts enabled). In this
case, a reception completion interrupt occurs when a message has been received and stored in mes-
sage buffer k-1, indicating that MBRB has become full. Alternatively, by clearing the IE bit of message
buffers 0 to (k-3) and setting the IE bit of message buffer k-2, a warning that MBRB is about to overflow
can be issued.
The basic conditions of storing receive data in each message buffer for the MBRB are the same as the
conditions of storing data in a single message buffer.
Cautions: 1. MBRB can be configured for each of the same message buffer types. Therefore,
Remark:
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2. MBRB does not have a ring buffer structure. Therefore, after a message is stored
3. MBRB operates based on the reception and storage conditions; there are no set-
4. With MBRB, “matching ID” means “matching ID after mask”. Even if the ID set to
n = 0, 1
m = 0 to 31
even if a message buffer of another MBRB whose ID matches but whose message
buffer type is different has a vacancy, the received message is not stored in that
message buffer, but instead discarded.
in the message buffer having the highest number in the MBRB configuration, a
newly received message will not be stored in the message buffer having the low-
est message buffer number.
tings dedicated to MBRB, such as function enable bits. By setting the same mes-
sage buffer type and ID to two or more message buffers, MBRB is automatically
configured.
each message buffer is not the same, if the ID that is masked by the mask register
matches, it is considered a matching ID and the buffer that has this ID is treated
as the storage destination of a message.
Chapter 16 FCAN Controller
User’s Manual U16702EE3V2UD00