TC1784
BootROM Content
User´s Manual
7-5
V1.1, 2011-05
BOOT_TC1784B, V1.21R12
7.4.3
CAN Bootstrap Loader
The CAN bootstrap loader transfers program code/data via node 0 of the MultiCAN
module into the PMI Scratchpad RAM. Data is transferred from the external host to the
TC1784 using eight-byte data frames. The number of data frames to be received is
programmable and determined by the 16-bit data message count value DMSGC.
The communication between TC1784 and external host is based on the following three
CAN standard frames:
•
Initialization frame - sent by the external host to the TC1784
•
Acknowledge frame - sent by the TC1784 to the external host
•
Data frame(s) - sent by the external host to the TC1784
The initialization frame is used in the TC1784 for baud rate detection. After a successful
baud rate detection is reported to the external host by sending the acknowledge frame,
data is transmitted using data frames.
Initialization Phase
The first task is to determine the CAN baud rate at which the external host is
communicating. This task requires the external host to send initialization frames
continuously to the TC1784. The first two data bytes of the initialization frame include a
2-byte baud rate detection pattern (5555
H
), an 11-bit (2-byte) identifier ACKID for the
acknowledge frame, a 16-bit data message count value DMSGC, and an 11-bit (2-byte)
identifier DMSGID to be used by the data frame(s).
The CAN baud rate is determined by analyzing the received baud rate detection pattern
(5555
H
) and the baud rate registers of the MultiCAN module are set accordingly. The
TC1784 is now ready to receive CAN frames with the baud rate of the external host.
Acknowledge Phase
In the acknowledge phase, the bootstrap loader waits until it receives the next correctly
recognized initialization frame from the external host, and acknowledges this frame by
generating a dominant bit in its ACK slot. Afterwards, the bootstrap loader transmits an
acknowledge frame back to the external host, indicating that it is now ready to receive
data frames. The acknowledge frame uses the message identifier ACKID that has been
received with the initialization frame.
Data Transmission Phase
In the data transmission phase, data frames are sent by the external host and received
by the TC1784. The data frames use the 11-bit data message identifier DMSGID that
has been sent with the initialization frame. Eight data bytes are transmitted with each
data frame. The first data byte is stored in PMI Scratchpad RAM starting from address
D400’0000
H
. Consecutive data bytes are stored at incrementing addresses.
Содержание TC1784
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