M16C29 Datasheet, PDF (474/499 Pages) Renesas Technology Corp – RENESAS MCU M16C FAMILY / M16C/Tiny SERIES

M16C/29 Group
22. Usage Notes
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.
Rev. 1.12 Mar.30, 2007 ^{page 450} of 458
REJ09B0101-0112