Wednesday, May 19, 2010

Bus access request - RQ/GT' maximum mode


Explain how external chip/IO devices request and control the system bus in maximum mode. Draw the corresponding timing diagram.


In maximum mode, the RQ'/GT' (request and grant) pin will play the important role. Whenever a device want access to the system bus, the device will lower RQ'/GT' for one cycle to request the access. After receiving the request, 8086/8088 will grant the access to system bus by also lowering the RQ'/GT' pin for one cycle.

Note that even though it is the same pin that being lowered at both occasion, the purpose is different

Request --> RQ' = 0' = 1= requesting access
Grant --> GT' = 0' = 1 = granting access

No comments:

Post a Comment

Popular Posts

Latest Post from my Other Blog