M16CSLASH29 datasheet(474/499 Pages) RENESAS

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22. Usage Notes

page 450

22.15.14 Definition of Programming/Erasure Times

"Number of programs and erasure" refers to the number of erasure per block.

If the number of program and erasure is n (n=100 1,000 10,000) each block can be erased n times.

For example, if a 2K byte block A is erased after writing 1 word data 1024 times, each to a different

address, this is counted as one program and erasure. However, data cannot be written to the same

adrress more than once without erasing the block. (Rewrite prohibited)

22.15.15 Flash Memory Version Electrical Characteristics 10,000 E/W cycle products (

Normal: U7, U9; T-ver./V-ver.: U7)

When Block A or B E/W cycles exceed 100, set the FMR17 bit in the FMR1 register to 1 (1 wait) to select

one wait state per block access for products U7 and U9. When the FMR17 bit is set to 1, one wait state is

inserted per access to Block A or B - regardless of the value of the PM17 bit. Wait state insertion during

access to all other blocks, as well as to internal RAM, is controlled by the PM17 bit - regardless of the

setting of the FMR17 bit.

To use the limited number of erasure efficiently, write to unused address within the block instead of

rewite. Erase block only after all possible address are used. For example, an 8-word program can be

written 128 times before erase becomes necessary.

Maintaining an equal number of erasure between Block A and B will also improve efficiency.

We recommend keeping track of the number of times erasure is used.

22.15.16 Boot Mode

An undefined value is sometimes output in the I/O port until the internal power supply becomes stable

_____________

when "H" is applied to the CNVSS pin and "L" is applied to the RESET pin.

When setting the CNVSS pin to "H", the following procedure is required:

____________

(1) Apply an "L" signal to the RESET pin and the CNVSS pin.

(2) Bring VCC to more than 2.7V, and wait at least 2 msec. (Internal power supply stable waiting time)

(3) Apply an "H" signal to the CNVSS pin.

____________

(4) Apply an "H" signal to the RESET pin.

When the CNVSS pin is “H” and RESET pin is “L”, P67 pin is connected to the pull-up resister.

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