Method and apparatus for generating sequence of multibit words
First Claim
1. A machine method of generating a sequence of m-bit multibit words selected from a set N of the words, wherein m is an integer, N is a substantially larger integer not exceeding 2m and the words are formed in succession in a plurality m of bistable devices, the method comprising the steps of:
- (a) storing a set n of change words each of which consists of a corresponding selection of change commands, where n is a plural integer substantially smaller than n,(b) addressing a sequence of the stored change words where said sequence is larger than n and at least some of said change words appear repeatedly in said sequence, and(c) applying each addressed change word to effect changes of state of selected ones of the bistable devices in accordance with the change commands included in such change word.
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Abstract
In automatic test equipment the logical levels on certain of the test pins are set to 0 and 1 by corresponding flip-flops included in respective I/O logic circuits. The states of the flip-flops (as well as other factors) are controlled by commands read out of a control RAM which is of sufficient width to provide a 4-bit command on lines for each logic circuit. The available commands include NOP commands and change commands which toggle the states of the corresponding flip-flops. A relatively small number of addresses of the control RAM have change commands entered in correspondence with selected ones of the pins. By repeatedly reading out the commands in these addresses in a non-cyclic sequence it is possible to generate a succession of different states of the flip-flops in the logic, which succession is much longer than the number of addresses of the control RAM which are utilized. Apparatus for establishing the correct addressing sequence is described.
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Citations
9 Claims
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1. A machine method of generating a sequence of m-bit multibit words selected from a set N of the words, wherein m is an integer, N is a substantially larger integer not exceeding 2m and the words are formed in succession in a plurality m of bistable devices, the method comprising the steps of:
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(a) storing a set n of change words each of which consists of a corresponding selection of change commands, where n is a plural integer substantially smaller than n, (b) addressing a sequence of the stored change words where said sequence is larger than n and at least some of said change words appear repeatedly in said sequence, and (c) applying each addressed change word to effect changes of state of selected ones of the bistable devices in accordance with the change commands included in such change word. - View Dependent Claims (2, 3, 4, 5)
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- 6. Apparatus for generating a sequence of m-bit multibit words, comprising a plurality m of bistable devices, a memory storing a set of change words, each of which consists of a corresponding selection of one or more change commands, means for reading out the change words in a succession in which at least some of the words are read out a plurality of times, and means for applying the change words to the bistable devices so that each said selection of change commands causes the or each device of the corresponding selection of devices to change state.
Specification