Z8
®
CPU
User Manual
UM001604-0108 Address Space
21
External Data Memory
The Z8 CPU, in some cases, can address up to 60 KB of external data memory beginning
at location 4096. External data memory (DM
) can be included with, or separated from, the
external Program Memory space. DM
, an optional I/O function that can be programmed to
appear on pin P34, is used to distinguish between data and Program Memory space. The
state of the DM
signal is controlled by the type of instruction being executed. An LDC
opcode references Program Memory (DM
inactive), and an LDE instruction references
data memory (DM
active Low). You must configure Port 3 Mode Register (P3M) bits D3
and D4 for this mode.
*Note: For additional information on using external memory, see Chapter 10 of this
manual. For exact memory addressing options available, see the device product
specification.
Figure 9. External Memory Map
External
65535
Memory
4096
Not Addressable
4095
0
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