AN2398 Freescale Semiconductor / Motorola, AN2398 Datasheet - Page 2

• Manufacturer Part Number: AN2398
• Description: In-Circuit Programming of FLASH Memory via the Universal Serial Bus for the MC68HC908JB8
• Manufacturer: Freescale Semiconductor / Motorola

AN2398/D
OVERVIEW AND MEMORY USAGE
2
In-Circuit Programming of FLASH Memory via the USB for the MC68HC908JB8
To use the USB interface as a communications link for ICP, the user code in
the JB8 must be modified to recognize some pre-defined USB commands for
ICP. Since the FLASH memory cannot be erased by code running in the same
area as it is being erased, the code must be loaded into RAM and executed
from RAM. The RAM size of 256-bytes in the JB8 is limited for the ICP scheme
described. Therefore, the following ICP method uses code that is pre-
programmed in an area of the JB8 memory. The user code is programmed to
the remainder of the FLASH memory and block erase routines are used to
erase the user code.
The JB8 must be initially programming with the ICP code in place, before it is
soldered onto the printed circuit board.
usage for the JB8 ICP scheme.
From
vectors block ranges from $FFF0 to $FFFF.
For this ICP scheme, the ICP code, from $F800 to $FBFF; and the user FLASH
vectors do not get reprogrammed in an ICP operation. These two blocks are
programmed before the JB8 is soldered onto the PCB. An ICP operation erases
and programs the FLASH memory from $DC00 to $F7FF (the shaded area
shown in
Freescale Semiconductor, Inc.
For More Information On This Product,
Figure
Figure
1, the user block ranges from $DC00 to $FBFF, and the user
Go to: www.freescale.com
Area that can be erased in ICP mode.
1).
Figure 1. FLASH Memory Usage for ICP
$DC00
$FBFF
$F7FE
$F7FF
$FFF0
$FFFF
$F800
:
Vectors redirection
User Code
ICP_FLAG
ICP Code
Figure 1
shows the FLASH memory
USER FLASH
MEMORY
USER FLASH
VECTORS
MOTOROLA