Renesas H8S/2100 Series Hardware Manual page 784

Section 24 Flash Memory
The difference between the programming procedures in user program mode and user boot mode is
whether the MAT is switched or not as shown in figure 24.14.
In user boot mode, the user boot MAT can be seen in the flash memory space with the user MAT
hidden in the background. The user MAT and user boot MAT are switched while the user MAT is
being programmed. Because the user boot MAT is hidden while the user MAT is being
programmed, the procedure program must be executed in an area other than flash memory. After
the user MAT programming completes, the user boot MATs cannot be selected again.
MAT switching is enabled by writing a specific value to FMATS. Note, however, that while the
MATs are being switched, the LSI is in an unstable state, e.g. access to a MAT is not allowed until
MAT switching is completed, and if an interrupt occurs, from which MAT the interrupt vector is
read is undetermined. Perform MAT switching in accordance with the description in section
24.10, Switching between User MAT and User Boot MAT.
Except for MAT switching, the programming procedure is the same as that in user program mode.
The area that can be executed in the steps of the user procedure program (on-chip RAM and user
MAT) is shown in section 24.8.4, Storable Areas for On-Chip Program and Program Data.
Rev. 1.00 May 09, 2008 Page 758 of 954
REJ09B0462-0100