The computer needs to be able to distinguish which of these cards information is coming from, and similarly each card needs to know when out going data is directed to it. To examine why, we need to investigate the structure of the PC.Įach of those back panel sockets is attached to a circuit board ( a card) which, like the internal devices, in turn plugs into a slot on the main circuit board. However, there is a practical limit to how much this can be done. Then why not just add more places to plug things into? This is quite possible, and has previously been the solution in many cases by installing more sockets, and even connecting devices internally to bypass the need for these plugs altogether.
While the above mentioned parallel and serial sockets can indeed be used by many different devices, they cannot be shared by more than one device at once, and so we can quickly run out of space to attach this new equipment. Today there is a huge range of peripheral equipment including scanners, digital cameras, specialised pointing devices, high speed modems, all of which need their own connection to the PC. However, recent technological developments have created problems for many users of PCs with this system. This system was quite suitable when it was implemented and has been used for many years. For example, mice use one that is dedicated to transmitting serial data, while printers usually use a parallel data cable, and monitors have their own special plug. Traditionally, computer hardware such as printers and mice were plugged into sockets on the back panel of a PC, with each connector being fairly specialised in its applications. Background : Why Replace Existing Technologies with USB?
However, it should still serve as a useful background or introductory note.
Things have changed a lot since then (e.g. This was originally a first year uni assignment, so it is limited in depth and the content is rather dated.
#Bit serial data interface bmw parts software#
The technical detail covers the system's logical structure, rather than the electrical or software characteristics. This document discusses what the USB system does and how it is done. Although not a relatively new development in personal computing, it has only recently gained popularity due to increasing software support. In quad mode, the software automatically distributes the data bytes among the IO lines using the same bit pattern depicted in Figure 8 above.USB is a system for connecting a wide range of peripherals to a computer, including pointing devices, displays, and data storage and communications products.
Note that were changing from 4-wire mode to quad mode in the middle of the transaction. Compare this to the 16 clock cycles required for our simple read transaction and its easy to see why quad mode is gaining popularity for high speed flash memory applications! To create this sequence in the SPI Exerciser command language, we would use the example code: 4m// Start in 4-wire mode sson// Activate slave select wt EB// Write instruction EBh qm// Switch to quad mode wt AA AA AA 00// Write 3-byte address and 8 read mode bits wt 55 55// Write 2 dummy bytes rd 2// Read two data bytesssoff// Deactivate slave select Quad mode fast read sequence for Spansion S25FL016K or equivalentĪfter the address cycle and dummy bytes have been sent by the host, the component begins sending data bytes each clock cycle consists of a data nibble spread across the 4 IO lines, for a total of two clock cycles per byte of data.
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