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A Controllable Skewer Using a Multiplexer Based Structure

IP.com Disclosure Number: IPCOM000021620D
Original Publication Date: 2004-Jan-28
Included in the Prior Art Database: 2004-Jan-28
Document File: 2 page(s) / 66K

Publishing Venue

IBM

Abstract

Skew control with a regular structure

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A Controllable Skewer Using a Multiplexer Based Structure

In applications like telecommunications, there are several protocols used to describe how to transfer data between two chips. Some of these protocols are using buses as the transmission media and they run at fast speed. In such conditions, it is often needed to have a mechanism to deskew the data transferred thereon that is due to mismatch in the bus path as shown in Figure 1. Another way of ensuring that the bus is correctly sampled at the receiver end is to control carefully the skew to com-pensate said mismatch as depicted in Figure
2. This control has to be programmable because of the different application/board designs. In the same way, to check that a chip designed to compensate the skew can really compensate any skew, it can be interesting to have a device capable of control-ling the skew in a bus.

  Hereafter there is described a mechanism to control the skew between any bit of a bus and also a very simple control to be used to add or remove skew. To that end, a repetitive base structure is used to construct the skewer. Each base structure is made of a buffer, a two-way multiplexer (mux) and an inverter at the output of the mux as illustrated in Figure 3. The input data (Data In) of the base struc-ture is directly connected to a first input of the mux and via the buffer to the second input thereof, so that depending on the control signal (Skew Control) that is applied to the control input of the mux, the output data (Data Out) is or is not delayed by the buffer. Note that, the inversion that is per-formed...