3.5
EZ-USB ROM Versions
The EZ-USB 8-KB Masked ROM and 32-KB Masked ROM memory maps are shown in
Figures 3-6 and 3-7.
Outside EZ-USB
Inside EZ-USB
FFFF
External
Data
Memory
(RD,WR)
External
Code
Memory
(PSEN)
8000
7B40
Registers(RD,WR)
(Note 1)
External
Data
Memory
(RD, WR)
2000
Internal Code
Memory(PSEN)
0800
07FF
0000
(Note 2)
Data (RD,WR)
(Note 1)
Note 1: OK to populate data memory here, but no RD# or WR# strobes are generated.
Note 2: OK to populate code memory here, but no PSEN# strobe is generated.
Figure 3-6. 8-KB ROM, 2-KB RAM Version
EZ-USB ROM versions contain program memory starting at 0x0000. In these versions,
the internal RAM is implemented as data-only memory.
Code for this ROM version can be developed and tested using the AN2131Q with an
external code memory (EA=1, Figure 3-5). As long as the 8051 limits internal RAM
access to 0x0000-0x07FF and accesses the EZ-USB registers and bulk data at 0x7B40-
0x7FFF, the code in the external memory will be the identical image of the code that will
ultimately be internal at 0x0000-0x1FFF in the ROM version.
EZ-USB TRM v1.9
Chapter 3. EZ-USB Memory
Page 3-7
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