Specifications

Developer’s Serial Bootloader, Rev. 13
FC protocol, version 4, ColdFire (V1)
Freescale Semiconductor28
• $03000 - Address of the relocated interrupt vector table.
• $001BC - Start address of the MCU interrupt vector table.
• $00400 - Length of the MCU erase blocks.
• $00080 - Length of the MCU write blocks.
• ‘MCF51JM128/USB’ - Identification string, zero terminated. Information to be displayed on the
PC screen.
6.2.4 Limitations
This section summarizes the limitations that must be considered when using the bootloader with the user
application.
6.2.4.1 Memory occupied
This version of bootloader limits the beginning of the flash memory. For this reason, the user must modify
the Linker Command File (LCF) and the boundary of the user flash start is moved to address 0x3800. The
following code example shows the LCF file for a user application.
# Sample Linker Command File for CodeWarrior for the ColdFire MCF51JM128
# Memory ranges
MEMORY {
application (RX) : ORIGIN = 0x00003800, LENGTH = 0x0001C7FF //memory allocation
userram (RWX) : ORIGIN = 0x00800000, LENGTH = 0x00003FFF
}
6.2.4.2 Delayed JMP instruction
The next limitation increases delays in the interrupts because there is a double jump instruction feature
being used. The complete situation is described in the following figure:
Figure 21. The vector redirection using the JMP instruction
IRQ INTERUPT
0x00000100
0x00003180
0x3180
0x4EF9
0x6000
JMP + address
IRQ interrupt
routine
0x6000