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Re: [usb] About nibble mode in USB Transceiver
** Proprietary **
hi Jiang,
i don't know much about the UTMI spec. but as far as my knowledge on bit unstuffing is concerned,
the bit unstuffer will first unstuff the serial data input and pass on the unstuffed data to the serial to parallel converter. also the bit unstuffer should have some extra control signal to indicate that the present bit is an unstuffed bit or not. say, in ur example that control signal should be high only during the 7th receiving bit('0'). when the serial-to-parallel converter receives the unstuffed serial input from bit unstuffer, it should check if the control signal is high or not at any point of time. if it's not high, then it will convert the serial input into nibble in four clock pulses. else it should wait for another clock pulse(a total of 5 clock pulses) if the control signal is high.
generally the above design is better but it's upto one to follow one's own.
hope u have understood.
....Vikas.
>>> jiangdaosan@21cn.com 06/25/02 08:14AM >>>
Hi,all:
I have a question in the nibble mode in USB Transceiver design.
In the USB Transceiver Module Specification(v1.04), there is a little about
nibble mode referred to in Page 10:
"For instance, serial data may be converted to a nibble-wide parallel format
immediately and handled as 4-bits data between the HS DLL and the RX Hold Register"
But as the bit unstuffer detected the sequence "1 1 1 1 1 1 0" and remove the last bit
"0", How can the bit unstuffer realized in the nibble-wide parallel format? and
how to output parallel data correctly according the spec? I was so puzzled about it.
Can anybody help me ? thanks in advance.
Any comments and advice are welcomed!
Best Regards.
================================
Jiang Daosan jiangdaosan@21cn.com
Institute of RF & OE IC
Southeastern University
NanJing Jiangsu China(210096)
Tel: 08625-3793303--8005
http://iroi.seu.edu.cn/
================================
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