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7-1
CHAPTER 7
CAN SERIAL COMMUNICATIONS CONTROLLER
The 87C196CB has a peripheral not found in the 8XC196NT — the CAN (controller area net-
work) peripheral. The CAN serial communications controller manages communications between
multiple network nodes. This integrated peripheral is similar to Intel’s standalone 82527 CAN
serial communications controller. It supports both the standard and the extended message frames
specified by CAN 2.0 protocol parts A and B developed by Robert Bosch, GmbH. This chapter
describes the integrated CAN controller and explains how to configure it. Consult Appendix A,
“Signal Descriptions,” for detailed descriptions of the signals discussed in this chapter.
7.1 CAN FUNCTIONAL OVERVIEW
The integrated CAN controller transfers messages between network nodes according to the CAN
protocol. The CAN protocol uses a multiple-master, contention-based bus configuration, which
is also called CSMA/CR (carrier sense, multiple access, with collision resolution). Each CAN
controller’s input and output pins are connected to a two-line CAN bus through which all com-
munication takes place (Figure 7-1).
Figure 7-1. A System Using CAN Controllers
196Cx
device
Engine
ABS
82527
82527
Transmission
Dashboard
196Cx
device
196Cx
device
CAN Bus
A2588-02
Bus
Driver
CPU
CPU
Tx0
Rx0
Tx0
Rx0
Bus
Driver
TXCAN
RXCAN
TXCAN
RXCAN
TXCAN
RXCAN
Bus
Driver
CAN_H
CAN_L
Bus
Driver
Bus
Driver
CAN_H
CAN_L
Security System
CAN_H
CAN_L
CAN_H
CAN_L
CAN_H
CAN_L
Bus
Bus