2. The PIEACK bit corresponding to the CAN module must be written with a 1, which can be accomplished with
the following C language statement:
PieCtrlRegs.PIEACK.bit.ACK9 = 1; // Enables PIE to drive a pulse into the CPU
3. The interrupt line into the CPU corresponding to the CAN module must be enabled, which can be
accomplished with the following C language statement:
IER |= 0x0100; // Enable INT9
4. The CPU interrupts must be enabled globally by clearing the INTM bit.
16.7.5 CAN Power-Down Mode
A local power-down mode has been implemented where the CAN module internal clock is deactivated by the
CAN module itself.
16.7.5.1 Entering and Exiting Local Power-Down Mode
During local power-down mode, the clock of the CAN module is turned off (by the CAN module itself) and only
the wake-up logic is still active. The other peripherals continue to operate normally.
The local power-down mode is requested by writing a 1 to the PDR (CANMC.11) bit, allowing transmission of
any packet in progress to complete. After the transmission is completed, the status bit PDA (CANES.3) is set.
This confirms that the CAN module has entered the power-down mode.
The value read on the CANES register is 0x08 (PDA bit is set). All other register read accesses deliver the value
0x00.
The module leaves the local power-down mode when the PDR bit is cleared or if any bus activity is detected on
the CAN bus line (if the wake-up-on bus activity is enabled).
The automatic wake-up-on bus activity can be enabled or disabled with the configuration bit WUBA of CANMC
register. If there is any activity on the CAN bus line, the module begins its power-up sequence. The module waits
until it detects 11 consecutive recessive bits on the CANRX pin and then it goes bus-active.
Note
The first CAN message, which initiates the bus activity, cannot be received. This means that the first
message received in power-down and automatic wake-up mode is lost.
After leaving the sleep mode, the PDR and PDA bits are cleared. The CAN error counters remain unchanged.
If the module is transmitting a message when the PDR bit is set, the transmission is continued until a successful
transmission, a lost arbitration, or an error condition on the CAN bus line occurs. Then, the PDA bit is activated
so the module causes no error condition on the CAN bus line.
To implement the local power-down mode, two separate clocks are used within the CAN module. One clock
stays active all the time to ensure power-down operation (that is, the wake-up logic and the write and read
access to the PDA (CANES.3) bit). The other clock is enabled depending on the setting of the PDR bit.
Controller Area Network (CAN)
1022
TMS320x2806x Microcontrollers
SPRUH18I – JANUARY 2011 – REVISED JUNE 2022
Copyright © 2022 Texas Instruments Incorporated
Содержание TMS320 2806 Series
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