Lucent Technologies MN10285K - Manual (Page 289)

ROM Correction
Description
Panasonic Semiconductor Development Company MN102H75K/F75K/85K/F85K LSI User Manual
288
Panasonic
12 ROM Correction
12.1 Description
The ROM correction function can correct the program data in any address within
the 256-kilobyte ROM. (It cannot correct OSD ROM data.) A maximum of
sixteen addresses can be corrected. Addresses are set as address match interrupts.
This function shortens time-to-market for large-scale designs, since changes can
be implemented in the software after the mask ROM is complete.
The ROM correction function has numerous other applications. For instance, you
can insert keywords into the functional routines, then use the function to send
internal status information to an external location. This enables system-level
examination of the internal status even with the mask ROM version.
To use the ROM correction function, embed a routine such as that shown in
figure 12-2 in the ROM.
As figure 12-1 shows, the function lies between the microcontroller and ROM
blocks. First set the correction data for any sixteen non-OSD addresses in the
ROM correction address match and data registers. (Follow the flow shown in
figure 12-2.) Once this is done, the circuit will correct the ROM output for the
designated addresses.
Figure 12-1 ROM Area Schematic Diagram Figure 12-2 ROM Correction Flow
ROM
address
CPU
ROM
correction
Instruction
counter Instruction
fetch
ROM
Start
Is ROM
correction
required?
Set up the
correction data
Enable the
correction function
Main
Necessary
software settings Yes
No