Datasheet

Section 7 ROM
Page 234 of 982 REJ09B0465-0300 Rev. 3.00
Sep 17, 2010
H8S/20103, H8S/20203, H8S/20223, H8S/20115, H8S/20215, H8S/20235 Group
(9) Frequent Reprogramming
For systems that will be frequently reprogrammed, follow the below procedure to reduce the
effective number of reprogramming operations. As far as is possible, write data at appropriately
increasing addresses until no blank areas remain, and then erase the whole block. For example, in
a case where the data are written in 16-byte sets, write the maximum of 256 16-byte sets, and then
erase the whole block when further reprogramming is required. This procedure can reduce the
effective number of reprogramming operations.
For control of the number of reprogramming operations, we recommend keeping a record of the
number of times each block has been reprogrammed.
(10) Occurrence of Erase Errors during Erasure Operation
When an erase error has occurred during an erasure operation, issue a clear-status command and
then an erasure command. Repeat this procedure at least three times so that the error does not
occur.
(11) Points for Caution when Using the Erase-Suspend Function
In CPU reprogramming mode, if the erase-suspend function is used during erasure of the user
ROM area, operations to erase the user ROM area will not be completed in some cases.
1. Conditions for the problem
In CPU reprogramming mode, repeated use of the erase-suspend function at a certain interval
within the period of erasure when the user ROM area is being erased in EW0 mode or EW1
mode
(1) EW0 mode
⎯ Repeated generation of interrupts with a certain interval
⎯ Repeated setting of the FMSPREQ bit in FLMCR2 to 1 with a certain interval
(2) EW1 mode
⎯ Repeated generation of interrupts with a certain interval
2. To avoid the problem
Do not use repeatedly the erase-suspend function at the certain interval. If the erase-suspend
function is to be repeatedly used within the period of erasure, employ software control to
ensure that the interval between requests satisfies the conditions given in formula 2-1 below to
avoid the same interval.
T2 > T1 + TD or T2 < T1 − TD (2-1)
⎯ TD = 1.0 μs (certain period that does not depend on the operating frequency of the product)
⎯ T1: Interval between previous and current requests for suspension of erasure
⎯ T2: Interval between current and next requests for suspension of erasure