Kontron Bootstrap Loader - Manual (Page 8)

Bootstrap Loader
Page 2 © PEP Modular Computers 2/98
2 System Operation
2.1 Startup
After system reset, the Bootstrap Loader is started. It searches the FLASH memory area for a valid start key. If this start
key is found, the Bootstrap Loader checks the 'BootWaitTime' from serial EEPROM or RTC. If the entry is valid, the con-
tinuation of the boot process is delayed by this time while flashing the green front panel LED to indicate that the system is
alive but waiting for continuation. If the entry is not valid, a default of 5 seconds is used. After the BootWaitTime has
passed, the program in FLASH is started.
The Bootstrap Loader has two modes of operation: non-interactive start mode as described above and the interactive com-
mand mode.
For normal board operation, only the non-interactive start mode is used to start a program in FLASH. This is done auto-
matically without any user interaction. The interactive command mode is used to re-program the FLASH memory contents
or change the BootWaitTime.
The serial term port operates at 9600 Baud, 8 bits / character, 1 stop bit and no parity.
2.2 Entering the Command Mode
There are two possible cases:
If no valid start key was found, the Bootstrap Loader's command mode is entered automatically
1)
.
If the user wants to enter the Bootstrap Loader manually (e.g. for re-programming the FLASH contents) he must use the
ABORT button on the front panel.
On CPUs without an ABORT button, the Bootstrap Loader will enter the command mode on detecting a BREAK character
of at least one second length at the terminal connector.
Note: The ABORT button must not be pushed until the green LED appears, because this button generates a NMI and the
exception vector tables must be initialized correctly to serve this NMI. Pressing the ABORT prior to the green LED leads
to HALT in most cases. In this case, press the RESET button and try again.
Note: The ABORT button must, however, be pushed before the green LED stops flashing (BootWaitTime), because system
control is passed to the downloaded binary image afterwards. The LED is cycled every 0.25 sec so if 1 second is specified
as BootWaitTime, the LED will only flash 2 times.
Note: CPUs without an user LED or without an ABORT button uses a BootWaitTime of at least 5 seconds.
CTRL-x deletes the complete input line while CTRL-a restores the last input line.
1)
The start key is a special combination of data appended at the end of the load program or inside the load program itself.