Abstract: A method for testing a series of functional blocks within an integrated circuit. Each of the functional blocks in the series is tested to determine a minimum parameter value and a maximum parameter value associated with each of the functional blocks. A minimum parameter delta value is calculated for each of the functional blocks in the series. The minimum parameter delta value is the minimum parameter value associated with a given one of the functional blocks subtracted from the minimum parameter value for a functional block immediately following the given one of the functional blocks in the series. A maximum parameter delta value is also calculated for each of the functional blocks in the series. The maximum parameter delta value is the maximum parameter value associated with the given one of the functional blocks subtracted from the maximum parameter value for the functional block immediately following the given one of the functional blocks in the series.

Abstract: A communications network comprising a hierarchy of communications systems all operating within the constraints of token ring protocols and operationally defining a single shared token ring. At least one of said systems is formed by a token ring hub as disclosed and claimed in our copending application 177,764 and is connected into a system comprising the next higher hierarchal level which may be another such token ring hub or a token ring LAN system. Each said hub has means for receiving a signal which indicates that the standard token ring protocols are satisfied with respect to the direct connection of the hub of a computer having a token ring adapter card fitted, or indicative of such a computer connected to another said hub at a lower level of the hierarchy.

Abstract: In a communications network, a portable token ring hub which serves as a computer communications network for a plurality of computers and answers to the protocol requirements of the computer adapter cards configured to a token ring topology and which also serves as an expander with respect to an installed token ring LAN. The hub comprises a plurality of input/output ports including respective sockets into each of which an adapter card of a respective computer plugs, a trunk insertion unit having an outlet port to which a wander lead and a trunk coupling device plug are connected, and an internal token ring which is normally a closed ring but into which each of the said input/output ports and the outlet port are inserted by means of relay contacts in accordance with the requirements of the token ring protocol.