7220 datasheet(116/303 Pages) RENESAS

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2-89

7220 Group User’s Manual

2.12 ROM correction function

Only the M37221M8-XXXSP and the M37221MA-XXXSP have this function.

This can correct ROM program data in ROM. Up to 2 addresses (2 blocks) can be corrected, a program for

correction is stored in the ROM correction memory in RAM. The ROM memory for correction is 32 bytes !

2 blocks.

Block 1 : addresses 02C016 to 02DF16

Block 2 : addresses 02E016 to 02FF16

Set an address of the ROM data to be corrected into the ROM correction address register. When the value

of the counter matches the ROM data address in the ROM correction address, the main program branches

to the correction program stored in the ROM correction memory. To return from the correction program to

the main program, the op code and operand of the JMP instruction (total of 3 bytes) are necessary at the

end of the correction program. When the blocks 1 and 2 are used in series, the above instruction is not

needed at the end of the block 1.

The ROM correction function is controlled by the ROM correction enable register.

Notes 1 : Specify the first address (op code address) of each instruction as the ROM correction address.

2 : Use the JMP instruction (total of 3 bytes) to return from

the correction program to the main program.

3 : Do not set the same address to ROM correction addresses 1 and 2 (addresses to 021716 to

021A16).

Fig. 2.12.1 ROM correction address registers

021716

ROM correction address 1 (high-order)

021816

ROM correction address 1 (low-order)

021916

ROM correction address 2 (high-order)

021A16

ROM correction address 2 (low-order)

Fig. 2.12.2 ROM correction enable register

b7 b6 b5 b4 b3 b2 b1 b0

ROM correction enable register (RCR) [Address 021216]

After reset RW

ROM Correction Enable Register

Block 1 enable bit (RCR0)

Name

Functions

0: Disabled

1: Enabled

Block 2 enable bit (RCR1)

0: Disabled

1: Enabled

Nothing is assigned. These bits are write disable bits. When

these bits are read out, the values are “0.”

2, 3 Fix these bits to “0.”

R—

FUNCTIONAL DESCRIPTION

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