ST10F271 datasheet(73/173 Pages) STMICROELECTRONICS

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ST10F271

CAN modules

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CAN modules

The two integrated CAN modules (CAN1 and CAN2) are identical and handle the

completely autonomous transmission and reception of CAN frames according to the CAN

specification V2.0 part B (active). It is based on the C-CAN specification.

Each on-chip CAN module can receive and transmit standard frames with 11-bit identifiers

as well as extended frames with 29-bit identifiers.

Because of duplication of the CAN controllers, the following adjustments are to be

considered:

●

Same internal register addresses of both CAN controllers, but with base addresses

differing in address bit A8; separate chip select for each CAN module. Refer to

Chapter 4: Memory organization on page 20.

●

The CAN1 transmit line (CAN1_TxD) is the alternate function of the Port P4.6 pin and

the receive line (CAN1_RxD) is the alternate function of the Port P4.5 pin.

●

The CAN2 transmit line (CAN2_TxD) is the alternate function of the Port P4.7 pin and

the receive line (CAN2_RxD) is the alternate function of the Port P4.4 pin.

●

Interrupt request lines of the CAN1 and CAN2 modules are connected to the XBUS

interrupt lines together with other X-Peripherals sharing the four vectors.

●

The CAN modules must be selected with corresponding CANxEN bit of XPERCON

●

The reset default configuration is: CAN1 enabled, CAN2 disabled.

Note:

If one or both CAN modules is used, Port 4 cannot be programmed to output all 8 segment

address lines. Thus, only four segment address lines can be used, reducing the external

memory space to 5 Mbytes (1 Mbyte per CS line).

17.1

Configuration support

It is possible that both CAN controllers are working on the same CAN bus, supporting

together up to 64 message objects. In this configuration, both receive signals and both

transmit signals are linked together when using the same CAN transceiver. This

configuration is especially supported by providing open drain outputs for the CAN1_Txd and

CAN2_TxD signals. The open drain function is controlled with the ODP4 register for port P4:

in this way it is possible to connect together P4.4 with P4.5 (receive lines) and P4.6 with

P4.7 (transmit lines configured to be configured as Open-Drain).

The user is also allowed to map internally both CAN modules on the same pins P4.5 and

P4.6. In this way, P4.4 and P4.7 may be used either as general purpose I/O lines, or used

for I2C interface. This is possible by setting bit CANPAR of XMISC register. To access this

17.2

CAN bus configurations

Depending on application, CAN bus configuration may be one single bus with a single or

multiple interfaces or a multiple bus with a single or multiple interfaces. The ST10F271 is

able to support these two cases.

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