Transmit History List Function - NEC V850E/PH2 User Manual

Priority Conditions
1 (high) Value of first 11 bits of ID
[ID28 to ID18]:
2 Frame type
3 ID type
4 Value of lower 18 bits of ID
[ID17 to ID0]:
5 (low) Message buffer number
Notes: 1. If the automatic block transmission request bit ABTTRG is set to 1 in the normal operation
mode with ABT, the TRQ bit is set to 1 only for one message buffer in the ABT message
buffer group.
If the ABT mode was triggered by ABTTRG bit (1), one TRQ bit is set to 1 in the ABT area
(buffer 0 through 7). Beyond this TRQ bit, the application can request transmissions (set
TRQ bit to 1) for other TX-message buffers that do not belong to the ABT area. In that case
an interval arbitration process (TX-search) evaluates all TX-message buffers with TRQ bit
set to 1 and chooses the message buffer that contains the highest prioritized identifier for
the next transmission. If there are 2 or more identifiers that have the highest priority (i.e.
identical identifiers), the message located at the lowest message buffer number is transmit-
ted at first.
Upon successful transmission of a message frame, the following operations are performed.
• The TRQ flag of the corresponding transmit message buffer is automatically cleared to 0.
• The transmission completion status bit CINTS0 of the CnINTS register is set to 1 (if the
interrupt enable bit (IE) of the corresponding transmit message buffer is set to 1).
• An interrupt request signal INTCnTRX is output (if the CIE0 bit of the CnIE register is set to
1 and if the interrupt enable bit (IE) of the corresponding transmit message buffer is set to
1).
2. When changing the contents of a transmit buffer, the RDY flag of this buffer must be cleared
before updating the buffer contents. As during internal transfer actions, the RDY flag may be
locked temporarily, the status of RDY must be checked by software, after changing it.

18.10.2 Transmit history list function

The transmit history list (THL) function records in the transmit history list the number of the transmit
message buffer from which data or remote frames have been were sent. The THL consists of storage
elements equivalent to up to seven messages, the last out-message pointer (LOPT) with the corre-
sponding CnLOPT register, and the transmit history list get pointer (TGPT) with the corresponding CnT-
GPT register.
The THL is undefined immediately after the transition of the CAN module from the initialization mode to
one of the operation modes.
The CnLOPT register holds the contents of the THL element indicated by the value of the LOPT pointer
minus 1. By reading the CnLOPT register, therefore, the number of the message buffer that transmitted
Chapter 18 AFCAN Controller
Description
The message frame with the lowest value represented by the first 11
bits of the ID is transmitted first. If the value of an 11-bit standard ID is
equal to or smaller than the first 11 bits of a 29-bit extended ID, the 11-
bit standard ID has a higher priority than a message frame with a 29-bit
extended ID.
A data frame with an 11-bit standard ID (RTR bit is cleared to 0) has a
higher priority than a remote frame with a standard ID and a message
frame with an extended ID.
A message frame with a standard ID (IDE bit is cleared to 0) has a
higher priority than a message frame with an extended ID.
If one or more transmission-pending extended ID message frame has
equal values in the first 11 bits of the ID and the same frame type (equal
RTR bit values), the message frame with the lowest value in the lower
18 bits of its extended ID is transmitted first.
If two or more message buffers request transmission of message
frames with the same ID, the message from the message buffer with the
lowest message buffer number is transmitted first.
User's Manual U16580EE3V1UD00 817