Converting from Intel 8x930Ax to Cypress EZ-USB
6
cam for video capture over the USB bus, while offering
high-quality video motion and video capture performance.
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 EZ-USB family.
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 I
2
C EEPROM for VID/PID, code
• Reconnect 1.5K D+ pull-up to DISCON
• 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 EZ-USB pin to indicate when the USB microcontroller
goes into a suspend state. CLK24 stops at the last known
state when EZ-USB goes into suspend.
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 EZ-USB, 24 Programmable I/O pins are available. This
provided enough Programmable I/O pins to allow the design-
er to eliminate the 16V8 PAL.
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 EZ-USB Turbo mode to increase the video
capture compression rate by 40%.
