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TC1796
System Units (Vol. 1 of 2)
Reset and Boot Operation
User’s Manual
4-24
V2.0, 2007-07
Reset, V2.0
4.4.2
Bootstrap Loader Mode 2 - CAN Boot via CAN Pins
The CAN boot mode of the bootstrap loader provides a mechanism to load program
code/data via the MultiCAN module into the SPRAM, and start executing the loaded
code from address D400 0000
H
(address of the first transmitted byte). A single data
frame always transmits eight code/data bytes from the external host to the TC1796. The
number of data frames to be received in CAN boot mode is programmable and depends
on the required amount of code/data to be transmitted. The 16-bit data message count
value DMSGC determines the number of code/data bytes to be transmitted as
8
×
MSGC with MSGC = 1 to 2
16
. Therefore, the 48 Kbyte SPRAM of the TC1796 can
be loaded completely during CAN boot mode.
The communication between TC1796 and external host is based on the following three
CAN standard frames:
•
Initialization frame - sent by the external host to the TC1796
•
Acknowledge frame - sent by the TC1796 to the external host
•
Data frame(s) - sent by the external host to the TC1796
The initialization frame is used in the TC1796 for baud rate detection. After a successful
baud rate detection is reported to the external host by the acknowledge frame, data is
transmitted by data frames.
shows the parameters and settings of the three
CAN standard frames used for CAN bootstrap loader.
Table 4-6
CAN Bootstrap Loader Frames
Frame Type
Parameter
Description
Initialization
Frame
Identifier
11-bit, don’t care
DLC = 8
Data length code, 8 bytes transmitted within CAN frame
Data byte 0
55
H
Data byte 1
55
H
Data byte 2
Acknowledge message identifier ACKID, low byte
Data byte 3
Acknowledge message identifier ACKID, high byte
Data byte 4
Data message count DMSGC, low byte
Data byte 5
Data message count DMSGC, high byte
Data byte 6
Data message identifier DMSGID, low byte
Data byte 7
Data message identifier DMSGID, high byte