ST72521R9-Auto STMicroelectronics, ST72521R9-Auto Datasheet - Page 201

• Manufacturer Part Number: ST72521R9-Auto
• Description: 8-bit MCU for automotive
• Manufacturer: STMicroelectronics

Specifications of ST72521R9-Auto

• Hdflash Endurance: 100 cycles, data retention 20 years
• Clock Sources: crystal/ceramic resonator oscillators, internal RC oscillator and bypass for external clock
• 4 Power Saving Modes: Halt, Active Halt, Wait and Slow

ST72521xx-Auto
Figure 79. Abort and transmission delayed by busy CAN bus
In this case the NRTX bit is set to abort the transmission after the first attempt. As the first
attempt is successful the READY and BUSY bits are reset by pCAN and the transmit buffer
becomes empty. An abort is no longer required.
Figure 80. Abort and error during transmission
In this case NRTX (abort request) is set before the error, thus pCAN resets READY and
BUSY after the error (the first attempt). The abort has been successful and the transmit
buffer is empty.
Figure 81. Abort and arbitration lost
In this case the NRTX bit is set but has no effect, as the previous transmission attempt failed
due to an arbitration lost. The application waits for the falling edge of BUSY bit and checks
that READY is still set. This is the case, this means pCAN has lost the arbitration and LOCK
bit can be safely reset. Abort is immediate and pCAN resets the READY and BUSY bits.
Timing considerations
As no interrupt signals that an abort has been successful, the application has to wait until
the transmit buffer is empty (transmission has been aborted or transmitted successfully).
This time can vary depending on the case in which the abort is performed (arbitration lost,
error or successful transmission). To show the impact of the software workaround on this
timing behavior
abort is done by LOCK only) with the behavior when NRTX, BUSY and LOCK bits are used.
Figure 82
TX RQST
ABORT RQST
CAN TX
CAN RX
LOCK
READY
BUSY
NRTX
TX RQST
ABORT RQST
CAN TX
CAN RX
LOCK
READY
BUSY
NRTX
TX RQST
ABORT RQST
CAN TX
CAN RX
LOCK
READY
BUSY
NRTX
and
Doc ID 17660 Rev 1
Figure 83
compare the reference behavior (worst case when
Error
Controller area network (CAN)
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