3.3
Expanding EZ-USB Memory
The 80-pin EZ-USB package provides a 16-bit address bus, an 8-bit bus, and memory
control signals PSEN#, RD#, and WR#. These signals are used to expand EZ-USB
memory.
Inside EZ-USB
Outside 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
1FFF
1F3F
Unused Bulk Buffers
(RD,WR)
(Note 1)
1B40
Code & Data
(Note 2)
(PSEN,RD,WR)
0000
Note 1: OK to populate data memory here--RD#, WR#, CS# and OE# pins are inactive.
Note 2: OK to populate code memory here--no PSEN# strobe is generated.
Figure 3-4. EZ-USB Memory Map with EA=0
Figure 3-4 shows that when EA=0, the code/data memory is internal at 0x0000-0x1B40.
External code memory can be added from 0x0000-0xFFFF, but it appears in the memory
map only at 0x1B40-0xFFFF. Addressing external code memory at 0x0000-0x1B3F
when EA=0 causes the EZ-USB core to inhibit the #PSEN strobe. This allows program
memory to be added from 0x0000-0xFFFF without requiring decoding to disable it
between 0x0000 and 0x1B3F.
Page 3-4
Chapter 3. EZ-USB Memory
EZ-USB TRM v1.9
CYPRESS [ CYPRESS ]
