VV0670P001 View Datasheet(PDF) - Vision
Part Name
Description
MFG CO.
'VV0670P001' PDF : 36 Pages View PDF
Colour Processor Interface ASIC
Details of Nibble Stream Mode Protocol
The figure below shows the details of the Nibble Stream Protocol. It shows two succesive bytes, A and B, being
transfered.
The host requests a byte bysetting nAutoFd to LO. CPiA will then present the lower nibble of the byte on the
4 status lines. It then sets nAck LO to signify that the data is ready. nAutoFd going HI causes the upper nibble
to be placed on the status lines and nAck is then taken HI to signify the data is ready for the host to read.
Figure 2.15 : Nibble Stream Mode Protocol
nFault
P
Data bit A:0
Data bit A:4
Data bit B:0
Data bit B:4
Select
P
Data bit A:1
Data bit A:5
Data bit B:1
Data bit B:5
PError
P
Data bit A:2
Data bit A:6
Data bit B:2
Data bit B:6
Busy
P
Data bit A:3
Data bit A:7
Data bit B:3
Data bit B:7
nAutoFd
H
nAck
P
2.2.5.16 Pass-Through Mode
• The CPiA device includes support for a parallel port pass-through mode of operation to allow another
parallel port device, e.g. a printer, to be daisy chained from a CPiA-based camera.
• The Windows 95/98 device driver supplied by VLSI Vision Ltd does not yet support his feature and so
only a brief description of the operation of this mode will be given here.
• Please contact Vision for more information.
Description of Pass-Through Mode Operation
The host can instruct the CPiA to enter pass-through mode by sending it a GotoPassThrough command. All
host control signals will then be echoed to the pass-through port and status signals from the pass-through
port will be echoed back to the host. In this mode the host has unrestricted access the pass-through device
and may use it as if the CPiA-based camera was not attached. While in this mode the CPiA will not attempt to
initiate communications with the host, or in anyway interfere with the host to pass-through device
communication that may be taking place.
When the host requires to communicate with CPiA, it must switch CPiA out of pass-through mode by sending
it a VPP(Vision Passthrough Packet) , which has a similar structure and signaling method as that defined in
the IEEE 1284.3 Draft Specification. This VPP packet is sent using only the 8 data lines without any strobing
or acknowledging on the control or status lines, this ensures that the pass-through device will not respond to
it.
V:\apps\cpia\docs\cpia datasheet\cpia_datasheet4.fm
02/07/98
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