TC1784
BootROM Content
User´s Manual
7-4
V1.1, 2011-05
BOOT_TC1784B, V1.21R12
Upon any other reset but not power-on, the clock configuration - respectively the system
frequency - remains the same as previously selected.
Next, depending on the Bootloader-type currently configured in HWCFG a pin is selected
as receive-data input (RxD) which will be evaluated on the following step. Note, that still
no further pin-configuration is done here - e.g. no assignment to a specific (ASC/CAN)
module functionality - but only the pin input-value is directly checked in this procedure.
The procedure waits to receive a low-level pulse at RxD and measures its duration - the
time between the falling and rising edges.
Then, the SSW checks the startup configuration in HWCFG:
•
upon ASC Bootloader Mode - a jump to the
routine
•
upon Generic Bootloader Mode - the type of interface (ASC/CAN) currently used
must be detected by the SSW. For this the RxD pin is checked until:
– low level is found there - then a jump to
) will be executed;
OR
– no edge is found for a time 6 time longer than the value in BL_meas - then
routine will be executed.
This interface-detection procedure is based on the following principles:
•
an ASC-Bootloader Host sends one only start Byte and then waits for a response
from the target system
•
a CAN-Bootloader Host sends a complete frame, whereas no more than 5
consecutive bits can be sent having equal logical levels - i.e. after two consecutive
edges for a given time dT, in any case another edge must follow within the next time-
frame of 6*dT.
7.4.2
ASC Bootstrap Loader
The ASC Bootloading routine implements the following steps:
•
RxD/TxD pins configuration is done in accordance to the TC1784 definitions, as well
as depending either the routine is invoked upon “ASC Bootloader”-startup mode
(ASC-only pins are used) or following an ASC-protocol detection upon “Generic
Bootloader”-mode (CAN/ASC-shared pins are used but configured to ASC module)
•
baudrate calculation is done based on the value already captured
•
ASC0 is initialized (without enabling the receiver) to the baudrate as determined, 8
data and 1 stop bit
•
acknowledge byte D5
H
is sent to the host indicating the device is ready to accept a
data transfer
•
after the acknowledge byte is transmitted, the receiver is enabled
•
the bootloader enters a loop waiting to receive exactly 128 bytes which are stored as
32 words in PMI Scratchpad RAM starting from address D400’0000
H
Once 128 bytes are received, the SSW starts the user code from address D400’0000
H
.
Содержание TC1784
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