Please confirm the following two points.
(1) The connection between SuperH microcomputer and synchronous DRAM.
H'FFFF 0000 →SuperH microcomputer's A15 pin ="0"
H'FFFF 8000 →SuperH microcomputer's A15 pin="1"
Please check to see if the A15 pin of SuperH microcomputer is connected to the synchronous DRAM.
If not, either address can be used.
(2) The mode register specification of synchronous DRAM.
For the mode register setting, it is necessary to use the address followed the mode register allocation of synchronous DRAM. Please confirm the correspondence of synchronous DRAM mode register bit connected to the A15 pin of SuperH microcomputer.