Converting from Intel 8x930Ax to Cypress EZ-USB
cam for video capture over the USB bus, while offering
The following schematic (Exhibit A) includes only the USB portion of the reference design. With added notes, this exam- ple illustrates the straightforward method of converting an In- tel 8x930Ax design to the
In performing this conversion, the following hardware chang- es were required.
•Remove boot EPROM
•Remove address/data latch (not needed)
•Remove 16V8 PAL
•Remove double width bus switch
•Add 3.3V regulator
•Add tiny I2C EEPROM for VID/PID, code
•Reconnect 1.5K D+
•Include RESET cap and resistor
The EXCLUSIVE ORs required to generate a suspend signal were eliminated as it is easier to use the CLK24 output pin of the
The use of an external address of the 8x930Ax only leaves 16 programmable I/Os for other functions. The 16V8 PAL is used to generate additional signals due to this limitation. With
The double width bus switch, isolating the USB microcontrol- ler from the video subsystem can be eliminated. The bus switch was incorporated to isolate the USB portion for the video subsystem in case it became inoperable due to ESD zap. Instead, substitute an ESD protection device specifically designed for USB. An example of an USB surge suppressor is TI’s SN75240PW which is rated to 8 KV.
Since MacWorld in Tokyo was only in 4 weeks from the start of their conversion process, Zoran was able to meet an accel- erated development schedule to complete both hardware and firmware conversion in time to make a press announcement at MacWorld. In addition, the board was much simpler, elimi- nating most all of the glue logic and external memory compo- nents surrounding the USB microcontroller. As a result, the system cost was reduced by 15%. Another added benefit was the improvement in performance. Zoran was able to take ad- vantage of the
6
