AN2283 Freescale Semiconductor / Motorola, AN2283 Datasheet - Page 8

• Manufacturer Part Number: AN2283
• Description: Scalable Controller Area Network (MSCAN)
• Manufacturer: Freescale Semiconductor / Motorola

AN2283/D
Transmission Process Overview
8
Motorola Scalable Controller Area Network (MSCAN) Interrupts
A structure can be created to refer to a particular row. The following example
structure shows a standard identifier being used.
/******* Transmit Header Table ***********/
typedef struct
{
volatile unsigned int ID:
volatile unsigned char DLC: 4;
volatile unsigned int *Data_Pointer;
} Transmit_Header;
Transmit_Header
Building on a good understanding of the transmit structure of the MSCAN, this
subsection will address the transmitting process of the MSCAN. There are two
registers involved in the transmit process:
The CTCR register consists of three bits: TXEIE2, TXEIE1, and TXEIE0 which
are the Transmitter Empty Interrupt Enable bits corresponding to the three
transmit buffers. If the user wishes to generate an interrupt to signal when a
transmit buffer has been emptied after a successful transmission, the bits
TXEIE2–TXEIE0 need to be enabled. This topic will be covered more in depth
in
The CTFLG register consists of three bits: TXE2, TXE1, and TXE0 that are the
Transmitter Buffer Empty bits for the corresponding three transmit buffers.
These bits will be set to 1 by the MSCAN when the associated message buffer
is emptied. When this occurs, the user can load a new message into the empty
transmit buffer. When a new message is ready for transmission, the associated
TXEx bit in the CTFLG register is cleared by the user changing the buffer state
to “transmit pending”. If more than one transmit buffer is ready for transmission,
the “local priority” of the buffers will determine which of them will be transmitted
first.
The MSCAN will now decide when the actual transmission onto the CAN bus
occurs and will perform the necessary arbitration and error checking.
Transmission
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Freescale Semiconductor, Inc.
For More Information On This Product,
MSCAN Transmitter Control Register (CTCR)
MSCAN Transmitter Flag Register (CTFLG)
Go to: www.freescale.com
Process.
Tx_Table [N];
16;
// This line refers to the
// number of rows (the number
// of messages N+1) in
// the table.
MOTOROLA