MC68HC908AS60ACFN FREESCALE [Freescale Semiconductor, Inc], MC68HC908AS60ACFN Datasheet - Page 270

• Manufacturer Part Number: MC68HC908AS60ACFN
• Description: M68HC08 Microcontrollers
• Manufacturer: FREESCALE [Freescale Semiconductor, Inc]

MSCAN Controller (MSCAN08)
An overrun condition occurs when both the foreground and the background receive message buffers are
filled with correctly received messages with accepted identifiers and another message is correctly
received from the bus with an accepted identifier. The latter message will be discarded and an error
interrupt with overrun indication will be generated if enabled. The MSCAN08 is still able to transmit
messages with both receive message buffers filled, but all incoming messages are discarded.
23.4.3 Transmit Structures
The MSCAN08 has a triple transmit buffer scheme to allow multiple messages to be set up in advance
and to achieve an optimized real-time performance. The three buffers are arranged as shown in
23-2.
All three buffers have a 13-byte data structure similar to the outline of the receive buffers (see
Programmer’s Model of Message
an 8-bit “local priority” field (PRIO) (see
270
MSCAN08
MC68HC908AZ60A • MC68HC908AS60A • MC68HC908AS60E Data Sheet, Rev. 6
Figure 23-2. User Model for Message Buffer Organization
Storage). An additional transmit buffer priority register (TBPR) contains
RxBG
RxFG
Tx0
Tx1
Tx2
23.12.5 Transmit Buffer Priority
PRIO
PRIO
PRIO
RXF
TXE
TXE
TXE
CPU08 Ibus
Registers).
Freescale Semiconductor
23.12
Figure