UPD784938 Datasheet, PDF (669/733 Pages) NEC – 16-Bit Single-Chip Microcontrollers

CHAPTER 27 ROM CORRECTION
27.4 Use of ROM Correction
<1> The correct address and post-correction instruction (correction program) are stored in the microcontroller external
non-volatile memory (EEPROM).
<2> A substitute instruction is read from the non-volatile memory with the use of a serial interface when the initialization
program is running after being reset, and this is stored in the peripheral RAM and external memory. The correction
channel is then selected, the address for the command that requires correction is read and set in the ROM correction
address registers (CORAH, CORAL), and the correction enable flag (COREN0 to 3) is set at 1. A maximum of four
locations can be set.
<3> Execute the CALLT instruction during execution of the corrected address.
Program execution (internal ROM)
No
Correct address executed?
Yes
CALLT execution
<4> CALLT routine branch
When matched with address pointer 0: CALLT table (0078H)
When matched with address pointer 1: CALLT table (007AH)
When matched with address pointer 2: CALLT table (007CH)
When matched with address pointer 3: CALLT table (007EH)
<5> Execute substitute instruction
<6> Add +3 to the stack pointer (SP)
<7> Restore to any addresses with the branch instruction (BR)
Preliminary User’s Manual U13987EJ1V0UM00
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