Z89175 Datasheet, PDF (31/68 Pages) Zilog, Inc. – Voice Processing Controllers

Zilog
Z89175/Z89176
Voice Processing Controllers
ROM Protect. The 24 KB of internal program memory for memory, and an LDE instruction references data (/DM ac-
the Z8 is mask programmable. A ROM protect feature pre- tive Low) memory.
vents “dumping” of the ROM contents of Program Memory
by inhibiting execution of LDC, LDCI, LDE, and LDEI in-
2
structions. The ROM Protect option is mask-programma-
ble, to be selected by the customer at the time the ROM
65535
code is submitted.
Data Memory (/DM). In ROM mode, the Z8 can address
up to 40 KB of external data memory beginning at location
24576 (Figure 18). In ROMless mode, the Z8 can address
the full 64 KB of external data memory beginning at loca-
tion 12. External data memory 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 Port 34, is used to distinguish between data and
program memory space (Table 5). The state of the /DM
signal is controlled by the type of instruction being execut-
ed. An LDC opcode references PROGRAM (/DM inactive)
External
Data
Memory
24575
Not Addressable
(In ROM Mode)
0
Figure 18. Data Memory Map
DS97TAD0100
PRELIMINARY
31