TMP88CS38 datasheet(39/226 Pages) TOSHIBA

39 / 226 page

TMP88CS38/CM38A/CP38A

2007-09-12

88CS38-39

1.7.3

Functions

The ROM corrective function can correct maximum four ROM areas with their

corresponding four banks of ROM corrective registers. Either program jump mode or data

replacement mode is selected for each bank by CM0 to CM3 respectively.

(1) Program jump mode

In the program jump mode, the system executes a jump instruction when the

program execution reaches the instruction at the corrective ROM address, skips from

the instruction which would have been executed, and executes an instruction at a

preset jump address.

Clearing ROMCCR CMx (x: 0 to 3) to “0” puts the system in the program jump mode.

Use ROMCDR to set the corrective ROM address and jump address.

When the start address of an erroneous program is a corrective ROM address, and

that of the patch program is a jump address, the bug in the erroneous program can be

fixed. Note that the patch program should end with a jump instruction, which causes a

return to the built-in ROM.

Note:

For program jump mode, the address to be corrected must be the start address of the

instruction.

Example 1: Setting the program correction circuit with the initial routine

Using the initial routine program, which is executed right after reset, set the

program correction circuit's register and stores the patch program into the built-in

RAM as follows.

1. Read the flag, which indicates whether to use the program correction circuit, from

the external memory.

2. If that circuit is not used, perform normal initial processing.

3. If it is used, clear CMx to 0 to establish the program jump mode.

4. Read the corrective ROM address and jump address from the external memory.

5. Set the corrective ROM address and jump address, which were read in step “4.”, in

ROMCDR.

6. Read the number of bytes for the patch program from the external memory.

7. Read the program with a number of bytes, equal to the byte count read in step “6.”,

from the external memory, and store that program into the built-in RAM.

8. Repeat steps “4.” through “7.” as many times as there are required banks.

Example 2: There is bugs on the locations from 0C020H to 0C085H

The corrective address, the jump vector, the program patch codes and other

information to patch the ROM with the bugs must be read out from any of memory

storage that holds them during initial program routine. CMn

= 0 specifies the

program jump mode. Subsequently, the patch program codes are loaded into RAM

(00600H to 006EFH). The start address (0C020H) of the ROM necessary to patch

is written to the corrective ROM address registers, and the start address (00600H)

of the RAM area to patch is loaded onto the jump address registers. When the

instruction at 0C020H is fetched, the instruction to jump into 00600H is

unconditionally executed instead of the instruction at 0C020H, and the

subsequent patch program codes are executed. The jump instruction at the end of

the patch program codes returns to the ROM at 0C086H.

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