access bus re access bus software creator s contest intro to access bus re the access bus software creator s contest announcement what is access bus access bus is a new open industry standard for computer peripheral connectivity access bus is a serial protocol that uses simple low cost i c technology to link multiple devices to a single pc port peripheral devices such as keyboards or keypads locators mice trackballs joysticks printers vr gloves digitizers sensors actuators or data transmitters and others can be easily daisy chained to the host pc applications such as cad cam data acquisition simulation virtual reality multiple player single pc games education and many many more can now take advantage of access bus the technology that puts plug and play on every pc the access bus offers advantages to end users and developers of systems and peripherals multiple devices connect to the host computer with only one port common communication methods for a number of device types lead to simplified hardware and software development as an open standard access bus enables cross platform use of the same device access bus technological description access bus technology is an open specification enabling anyone to implement it on host systems or in peripheral devices without fee or royalty access bus has a bus topology architecture that is a single host can accommodate up to peripheral devices access bus data rate is kbits sec access bus physical layer access bus is a serial bus architecture based on i c hardware protocol with one data line and one clock line standard low cost i c microcontrollers handle bit level handshaking including automatic arbitration and clock synchronization access bus software protocols the access bus communication protocol is composed of three levels i c protocol base protocol and application protocol i c protocol this simple and efficient protocol defines arbitration among contending masters without losing data i c provides for cooperative synchronization of bus partners with different clock rates bus transactions include addressing framing of bits into bytes and byte acknowledgment by the receiver base protocol establishes the asymmetrical interconnect between a host computer and multiple peripherals the host becomes the access bus manager the base protocol defines the format of an access bus message envelope which is an i c bus transaction with additional semantics including checksum unique features of the base protocol are auto addressing and hot plugging auto addressing assigns devices with unique bus addresses without the need for setting jumpers or switches hot plugging is the ability to attach and detach devices while the system is running without rebooting application protocol this is the highest level of the access bus protocol which defines message semantics specific to particular types of devices each type requires a different application protocol three broad device types have been identified keyboards locators and text devices access bus support on the pc all three levels of the access bus protocol are supported on the pc an add on card implements the physical layer and uses the base protocol to communicate with physical access bus devices an access bus manager tsr under dos and a dll under windows controls the operation of the physical layer and interacts with the access bus device drivers drivers are available for multiple access bus keyboards locators and printers for dos and windows also available are c language source code examples of the interface from applications to the device drivers to contact abig the access bus industry group postal address altair way suite sunnyvale ca internet email abig netcom com fax voice
