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1
SDA LINE
0
0
1
ST
ART
0 0 0 1 0
READ
ACK
ACK
NO ACK
STOP
Device
Address
DATA BYTE n
DATA BYTE n+1
2.19 eCAN Boot Function
280x
target
#1
#n
target
280x
CAN
host
CAN bus
eCAN Boot Function
Figure 2-25. Sequential Read
The eCAN bootloader asynchronously transfers code from eCAN-A to internal memory. The host can be
any CAN node. The communication is first done with 11-bit standard identifiers (with a MSGID of 0x1)
using two bytes per data frame. The host can download a kernel to reconfigure the eCAN if higher data
throughput is desired.
Figure 2-26. Overview of eCAN-A bootloader Operation
The bit-timing registers are programmed in such a way that a valid bit-rate is achieved for different
XCLKIN values as shown in
Table 2-8. Bit-Rate Values for Different XCLKIN Values
XCLKIN
SYSCLKOUT
Bit Rate
40 MHz
20 MHz
1 Mbps
20 MHz
10 MHz
500 kbps
10 MHz
5 MHz
250 kbps
5 MHz
2.5 MHz
125 kbps
The SYSCLKOUT values shown are the reset values with the default PLL setting. The BRP
reg
and bit-time
values are hard coded to 1 and 10, respectively.
Mailbox 1 is programmed with a standard MSGID of 0x1 for boot-loader communication. The CAN host
should transmit only 2 bytes at a time, LSB first and MSB next. For example, to transmit the word 0x08AA
to the 280x, transmit AA first, followed by 08. The program flow of the CAN bootloader is identical to the
SCI bootloader. The data sequence for the CAN bootloader shown in
:
SPRU722C – November 2004 – Revised October 2006
Bootloader Features
45
