The MC68HC11 expanded mode circuits
Orgler electronic
"Applications with microcontroller HC11"

exaddr.gif The address space of 68HC11 is 64K from $0000 to $FFFF
This address space is divided in internal and
external memory portions.
For the external memory a circuit with 74HC138
mades this possible suddivision.

exdecode.GIF Decode circuit with HC138
for eprom with maxsize of 32K (27C256)
and RAM with maxsize of 16K
8 * Read and 8 * WRITE

exmemory.gif Eprom and RAM

exlcd.gif LCD circuit
The WRITE-signal must be inverted