s908gz60cfa Freescale Semiconductor, Inc, s908gz60cfa Datasheet - Page 137

• Manufacturer Part Number: s908gz60cfa
• Description: M68hc08 Microcontrollers
• Manufacturer: Freescale Semiconductor, Inc

12.3 External Pins
The MSCAN08 uses two external pins, one input (CAN
pin represents the logic level on the CAN: 0 is for a dominant state, and 1 is for a recessive state.
A typical CAN system with MSCAN08 is shown in
Each CAN station is connected physically to the CAN bus lines through a transceiver chip. The
transceiver is capable of driving the large current needed for the CAN and has current protection against
defected CAN or defected stations.
12.4 Message Storage
MSCAN08 facilitates a sophisticated message storage system which addresses the requirements of a
broad range of network applications.
12.4.1 Background
Modern application layer software is built under two fundamental assumptions:
Above behavior cannot be achieved with a single transmit buffer. That buffer must be reloaded right after
the previous message has been sent. This loading process lasts a definite amount of time and has to be
Freescale Semiconductor
1. Any CAN node is able to send out a stream of scheduled messages without releasing the bus
2. The internal message queue within any CAN node is organized as such that the highest priority
between two messages. Such nodes will arbitrate for the bus right after sending the previous
message and will only release the bus in case of lost arbitration.
message will be sent out first if more than one message is ready to be sent.
MC68HC908GZ60 • MC68HC908GZ48 • MC68HC908GZ32 Data Sheet, Rev. 6
CAN_H
CAN NODE 1
CAN
TRANSCEIVER
MCU
CAN CONTROLLER
TX
Figure 12-2. The CAN System
(MSCAN08)
CAN
CAN_L
RX
C A N BUS
Figure
CAN STATION 1
RX
CAN NODE 2
12-2.
) and one output (CAN
CAN NODE N
TX
). The CAN
External Pins
TX
output
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