HD64F36034 datasheet(360/592 Pages) RENESAS

360 / 592 page

Section 15 Controller Area Network for Tiny (TinyCAN)

Rev. 4.00 Mar. 15, 2006 Page 328 of 556

REJ09B0026-0400

Internal Arbitration at Transmission: The TinyCAN transmits untransmitted messages in the

priority order from Mailbox 3 to Mailbox 1. The internal arbitration function selects the Mailbox

with the highest priority among all transmission request messages. Internal arbitration is based on

the three sources given below.

• TXPR/TXCR is set

• Arbitration lost during message transmission

• CAN bus error

TXPR/TXCR Setting: Figure 15.7 shows the timing of the TinyCAN internal arbitration caused

by the TXPR/TXCR setting. Transmit procedure and operation are as follows.

1. Write data of a transmit message to MCn0, MCn4 to MCn7, and MDn0 to MDn7 [n = 1 to 3]

before clearing the MBn bit in MBCR corresponding to the Mailbox of the transmit message to

0 (initial setting).

2. Set the corresponding MBn bit in TXPR to 1 (start condition issuance). Then, the start

condition is generated.

3. The internal arbitration for message 1 is determined and the transmit message is transferred to

the temporary buffer. After that, even if a transmit request cancellation is issued to the message

being transmitted by the DART or MBn bit in TXCR, message 1 is transmitted continuously

unless the TinyCAN detects an arbitration loss or error on the CAN bus.

4. After the seventh bit of the EOF has been transmitted (normal message transmission end), the

MBn bits in TXPR and TXCR which are corresponding Mailbox are cleared to 0 and the MBn

bit in TXACK and the EMPI bit in TCIRR1 are set to 1. At this time, the MBn bit in ABACK

is always 0. Then, message transmission is completed.

5. When there is a transmit request other than for message 1, the transmit message is transferred

to the temporary buffer and transmitted to the CAN bus after the arbitration for message 2 has

been determined. When there is no transmit request other than for message 1, the TinyCAN

performs reception.

HD64F36034 Datasheet(PDF) 360 Page - Renesas Technology Corp