C281x eCAN Transmit - Enhanced Control Area Network transmit mailbox

Library

Embedded Coder/ Embedded Targets/ Processors/ Texas Instruments C2000/ C281x

Description

The C281x enhanced Control Area Network (eCAN) Transmit block generates source code for transmitting eCAN messages through an eCAN mailbox. The eCAN module on the DSP chip provides serial communication capability and has 32 mailboxes configurable for receive or transmit. The C28x supports eCAN data frames in standard or extended format.

Note   Fixed-point inputs are not supported for this block.

Data Vectors

The length of the vector for each transmitted mailbox message is 8 bytes. Input data are always right-aligned in the message data buffer. Only uint16 (vector length = 4 elements) or uint32 (vector length = 2 elements) data are accepted. The following examples show how the different types of input data are aligned in the data buffer

For input of type uint32,

inputdata [0] = 0x12345678

the data buffer is:

data buffer[0] = 0x78
data buffer[1] = 0x56
data buffer[2] = 0x34
data buffer[3] = 0x12
data buffer[4] = 0x00
data buffer[5] = 0x00
data buffer[6] = 0x00
data buffer[7] = 0x00

For input of type uint16,

inputdata [0] = 0x1234

the data buffer is:

data buffer[0] = 0x34
data buffer[1] = 0x12
data buffer[2] = 0x00
data buffer[3] = 0x00
data buffer[4] = 0x00
data buffer[5] = 0x00
data buffer[6] = 0x00
data buffer[7] = 0x00

For input of type uint16[2], which is a two-element vector,

inputdata [0] = 0x1234
inputdata [1] = 0x5678

the data buffer is:

data buffer[0] = 0x34
data buffer[1] = 0x12
data buffer[2] = 0x78
data buffer[3] = 0x56
data buffer[4] = 0x00
data buffer[5] = 0x00
data buffer[6] = 0x00
data buffer[7] = 0x00

Dialog Box

Mailbox number

Unique number between 0 and 15 for standard or between 0 and 31 for enhanced CAN mode. It refers to a mailbox area in RAM. In standard mode, the mailbox number determines priority.

Message identifier

Identifier of length 11 bits for standard frame size or length 29 bits for extended frame size in decimal, binary, or hex. If in binary or hex, use bin2dec(' ') or hex2dec(' '), respectively, to convert the entry. The message identifier is coded into a message that is sent to the CAN bus.

Message type

Select Standard (11-bit identifier) or Extended (29-bit identifier).

Enable blocking mode

If selected, the CAN block code waits indefinitely for a transmit (XMT) acknowledge. If cleared, the CAN block code does not wait for a transmit (XMT) acknowledge, which is useful when the hardware might fail to acknowledge transmissions.

Post interrupt when message is transmitted

If selected, an asynchronous interrupt is posted when data is transmitted.

Interrupt Line

Select the interrupt line the asynchronous interrupt uses, 0 or 1.

Note   For information about setting the timing parameters of the CAN module, see Configuring Timing Parameters for CAN Blocks.

References

For detailed information on the eCAN module, see TMS320F28x DSP Enhanced Control Area Network (eCAN) Reference Guide, Literature Number SPRU074A, available at the Texas Instruments Web site.

See Also

C281x eCAN Receive

eCAN_A, eCAN_B

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