Cypress Semiconductor FX2LP Installationsanleitung PDF herunterladen (Seite 18)

EZ-USB Development Kit Manual - Getting Started

Page -14 EZ-USB Development Kit Manual - Getting Started Rev 1.0

– The third column, “Ext Flash”, allows a flash memory (or other ROM) to be connected to the

8051 bus. This is the only configuration that starts 8051 execution from external memory (the

GAL sets EA=1). Since external memory occupies the bottom 16K, the internal EZ-USB RAM

is addressed only as data memory, instead of combined prog/data memory in the other three

configurations.

– The fourth column, “Single Chip”, disables all external memory. This configuration is useful

for testing final code to insure that it uses no external resources present in the development

environment.

4.9 I

C Expanders

U8 and U10 are Philips PCF8574 I/O expanders. They connect to the I

C bus SCL and SDA pins,

and provide 8 general-purpose input-output pins. U8 provides 8 output bits, connected to the

seven-segment readout U9. U10 provides 8 input bits, four of which connect to push buttons S2-

S5, and four of which are uncommitted.

U8 connects to the 7-segment readout (U9) using the following bit assignments:

U8 has the group address 0100, and is strapped to unit address 001. Therefore to write a value to

the 7-segment readout, 8051 firmware sends a control byte of 01000010 (the LSB indicates a

write operation), followed by the data byte.

U10 uses its I/O pins as inputs, connected to S2-S5 according to the following table:

bit 0

bit 6

bit 3

bit 1bit 2

bit 4 bit 5

bit 7

1 2 ... 13 14 15 16 17 18 19 20 21 22 23 ... 27 28

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Cypress Semiconductor FX2LP Installationsanleitung Seite 18