TC1796
System Units (Vol. 1 of 2)
Reset and Boot Operation
User’s Manual 4-20 V2.0, 2007-07
Reset, V2.0
4.4 Bootstrap Loader (BSL)
The bootstrap loader (BSL) is a software part which is integrated in the TC1796 Boot
ROM. The BSL provides a mechanism to load a program code via a serial interface (ASC
or CAN) into the scratchpad RAM (SPRAM) of the PMI. After loading of the code, the
BSL jumps directly to address D400 0000
H
(start address of the PMI scratchpad RAM)
and begins executing the program code that has been loaded. The BSL automatically
calculates the baud rate of the serial data streams.
Table 4-5 shows the three BSL modes with its parameters.
With the low-to-high signal transition of the hardware reset signal HDRST or the power-
on reset signal PORST, the input pins BRKIN and HWCFG[3:0] of the TC1796 are
latched. If one of the latched BRKIN/HWCFG[3:0] signal combination of Table 4-5 is
detected, the bootstrap loader is started and the selected bootstrap loader mode is
entered.
The bootstrap loader can also be started by a software reset. For this purpose, bit
RST_REQ.SWBRKIN and bit field RST_REQ.SWCFG must be loaded with the
corresponding BRKIN/HWCFG[3:0] code, and bit RST_REQ.SWBOOT must be set (see
also RST_REQ register description at Page 4-5).
When a boot option for a bootstrap loader mode is detected, the TC1796 jumps to
address DFFF FFFC
H
which is the last word address of the Boot ROM. During execution
of the bootstrap loader, the Watchdog Timer interrupts and NMI interrupts are disabled.
Table 4-5 Bootstrap Loader Selections
Bootstrap Loader Mode Selection
1)
1) The bootstrap loader mode selections in alternate boot modes see Table 4-3.
Associated I/O Lines
BRKIN HWCFG
[3:0]
Receive Transmit
Bootstrap Loader Mode 1 (BSL1):
ASC Boot via ASC0 Pins
1 0000
B
P5.0 /
RXD0A
P5.1 /
TXD0A
Bootstrap Loader Mode 2 (BSL2):
CAN Boot
0001
B
P6.8 /
RXDCAN0
P6.9 /
TXDCAN0
Bootstrap Loader Mode 3 (BSL3):
ASC Boot via CAN Pins
1111
B
P6.8 /
RXD0B
P6.9 /
TXD0B
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