National CP3BT26 Dress, as shown in Figure, Listen Only bit can be used to configure, Ignack

CP3BT26

Sequence of Data Bytes on the Bus

ID

Data1

Data2

Data3

Data4

Data5

Data6

Data7

Data8

CRC

t

Storage of Data Bytes

ADDR Offset

Data Bytes

in the Buffer Memory

0A16

Data1

Data2

0816

Data3

Data4

0616

Data5

Data6

0416

Data7

Data8

DS045

Figure 61. Data Direction Bit Clear

Setting the DDIR bit will cause the direction of the data stor-

highest address and the first byte is stored at the lowest ad-

age to be reversed — the last byte received is stored at the

dress, as shown in Figure 62.

Sequence of Data Bytes on the Bus

ID

Data1

Data2

Data3

Data4

Data5

Data6

Data7

Data8

CRC

t

Storage of Data Bytes

ADDR Offset

Data Bytes

in the Buffer Memory

0A16

Data8

Data7

0816

Data6

Data5

0616

Data4

Data3

0416

Data2

Data1

DS046

Figure 62. Data Direction Bit Set

LO

The Listen Only bit can be used to configure

IGNACK

When the Ignore Acknowledge bit is set, the

the CAN interface to behave only as a receiv-

CAN module does not expect to receive a

er. This means:

dominant ACK bit to indicate the validity of a

•

Cannot transmit any message.

transmitted message. It will not send an error

•

Cannot send a dominant ACK bit.

frame when the transmitted frame is not ac-

•

When errors are detected on the bus, the

knowledged by any other CAN node. This fea-

CAN module will behave as in the error

ture can be used in conjunction with the

passive mode.

LOOPBACK bit for stand-alone tests outside

Using this listen only function, the CAN inter-

of a CAN network.

face can be adjusted for connecting to an op-

0 – Normal mode.

erating network with unknown bus speed.

1 – The CAN module does not expect to re-

0 – Transmit/receive mode.

ceive a dominant ACK bit to indicate the

1 – Listen-only mode.

validity of a transmitted message.

LOOPBACK

When the Loopback bit is set, all messages

sent by the CAN module can also be received

by a CAN module buffer with a matching buff- er ID. However, the CAN module does not ac- knowledge a message sent by itself. Therefore, the CAN module will send an error frame when no other device connected to the bus has acknowledged the message.

0 – No loopback.

1 – Loopback enabled.

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