Hitachi H8/3937 Series Hardware Manual page 134

Note: * The output data is not guaranteed if this address area is read in PROM mode. Therefore,
when programming with a PROM programmer, be sure to specify addresses from H'0000
to H'EDFF. If programming is inadvertently performed from H'EE00 onward, it may not be
possible to continue PROM programming and verification.
When programming, H'FF should be set as the data in this address area (H'EE00 to
H'1FFFF).
Figure 6-3 H8/3937 and H8/3937R Memory Map in PROM Mode
122
Address in
MCU mode
H'0000
On-chip PROM
H'EDFF
Uninstalled area*
Address in
PROM mode
H'0000
H'EDFF
H'1FFFF