Single-Shot Mode; Self-Test Mode - NEC V850E/PH2 User Manual

18.13.2 Single-shot mode

In the single-shot mode, automatic re-transmission as defined in the CAN protocol is switched off.
(According to the CAN protocol, a message frame transmission that has been aborted by either arbitra-
tion loss or error occurrence has to be repeated without control by software.) All other behavior of single
shot mode is identical to normal operation mode. Features of single shot mode can not be used in com-
bination with normal mode with ABT.
The single-shot mode disables the re-transmission of an aborted message frame transmission
according to the setting of the AL bit of the CnCTRL register. When the AL bit is cleared to 0, re-
transmission upon arbitration loss and upon error occurrence is disabled. If the AL bit is set to 1, re-
transmission upon error occurrence is disabled, but re-transmission upon arbitration loss is enabled. As
a consequence, the TRQ bit in a message buffer defined as a transmit message buffer is cleared to 0
by the following events:
• Successful transmission of the message frame
• Arbitration loss while sending the message frame
• Error occurrence while sending the message frame
The events arbitration loss and error occurrence can be distinguished by checking the CINTS4 and
CINTS3 bits of the CnINTS register respectively, and the type of the error can be identified by reading
the LEC[2:0] bits of the CnLEC register.
Upon successful transmission of the message frame, the transmit completion interrupt bit CINTS0 of
the CnINTS register is set to 1. If the CIE0 bit of the CnIE register is set to 1 at this time, an interrupt
request signal is output.
The single-shot mode can be used when emulating time-triggered communication methods (e.g.,
TTCAN level 1).
Caution

18.13.3 Self-test mode

In the self-test mode, message frame transmission and message frame reception can be tested without
connecting the CAN node to the CAN bus or without affecting the CAN bus.
In the self-test mode, the CAN module is completely disconnected from the CAN bus, but transmission
and reception are internally looped back. The CAN transmission pin (CTXDn) is fixed to the recessive
level.
If the falling edge on the CAN reception pin (CRXDn) is detected after the CAN module has entered the
CAN sleep mode from the self-test mode, however, the module is released from the CAN sleep mode in
the same manner as the other operation modes. To keep the module in the CAN sleep mode, use the
CAN reception pin (CRXDn) as a port pin.
Chapter 18 AFCAN Controller
operating in the receive-only mode, there is no ACK on the CAN bus. Due to
the missing ACK, the transmitting node will transmit an active error flag, and
repeat transmitting a message frame. The transmitting node becomes error
passive after transmitting the message frame 16 times (assuming that the error
counter was 0 in the beginning and no other errors have occurred). After the
message frame for the 17th time is transmitted, the transmitting node
generates a passive error flag. The receiving node in the receive-only mode
detects the first valid message frame at this point, and the VALID bit is set to 1
for the first time.
The AL bit is only valid in Single-shot mode. It does not influence the operation
of re-transmission upon arbitration loss in the other operation modes.
User's Manual U16580EE3V1UD00 829