Field programmable device having test provisions for fault detection

• US 4,320,507 A
• Filed: 11/19/1979
• Issued: 03/16/1982
• Est. Priority Date: 11/25/1978
• Status: Expired due to Term

• Current Assignee: Fujitsu Limited
• Original Assignee: Fujitsu Limited
• Inventors: Ueno, Kouji, Koyama, Kazumi, Fukushima, Toshitaka
• Primary Examiner(s): Malzahn, David H.
• Application Number:
  US06/095,782
• Time in Patent Office: 848 Days
• Field of Search: 371/21, 371/51, 365/201, 324/73 R
• US Class Current: 714/721
• CPC Class Codes: G11C 29/24 Accessing extra cells, e.g. dummy cells or redundant cells
• CPC Class Codes: G11C 29/52 Protection of memory contents; Detection of errors in memory contents

Abstract

A field programmable device having a memory cell member including regular bit lines, regular word lines, regular memory cells connected at the cross points of said regular bit lines and regular word lines, test bit or test word lines, and non-conductive and conductive test memory cells connected at the cross points of said regular bit or regular word lines and test word or test bit lines, wherein the conductivity of a test memory cell is determined by the "1" or "0" of the address signal by which the test word or test bit line to which the test memory cell is connected is selected.

Claims

1. A field programmable device having a memory array member comprising:

a plurality of regular bit lines,

a plurality of regular word lines defining cross points with said plurality of regular bit lines,

regular memory cells connected at respectively associated cross points between said plurality of regular bit lines and said plurality of regular word lines,

at least one test line adjacent a corresponding one of said pluralities of said regular bit lines and said regular word lines and defining cross points with the lines of the other of said pluralities of regular bit lines and regular word lines,

test memory cells respectively connected at the said cross points of said at least one test line and said lines of the said other of said pluralities of regular bit lines and regular word lines,

means for selectively supplying address signals of "1" and "0" levels for selecting respectively corresponding ones of said lines of the said other of said pluralities of regular bit lines and regular word lines, and

said test memory cells comprising non-conductive test memory cells connected at the said cross points with said corresponding lines of the said other of said pluralities of said regular bit and said regular word lines selected by a "0" level address signal, and conductive test memory cells connected at the cross points with said lines of the said other of said pluralities of said regular bit and said regular word lines selected by a "1" level address signal.

2. A field programmable device as recited in claim 1 wherein said other of said pluralities of regular bit lines and regular word lines includes additional said regular lines selected by an Nth address signal beyond said address signal having said "0" and "1" levels, and wherein:

said test memory cells are connected at the said cross points of said at least one test line and said additional said regular lines of said other of said pluralities and have an order of conductivity for the Nth address signal which is the reverse of the order of conductivity of the test memory cells connected to said regular lines of said other of said pluralities corresponding to the first through the (N-1)th address signals.

3. A field programmable device as defined in claim 1 comprising:

at least a second test line adjacent said corresponding one of said pluralities of said regular bit lines and said regular word lines and defining respective cross points with the lines of said other of said pluralities of regular bit lines and regular word lines,

test memory cells respectively connected at the said cross points of said second test line and said lines of said other of said pluralities of regular bit lines and regular word lines, and wherein said test memory cells respectively connected at the said respective cross points of said second test line are of the opposite conductivity type to the test memory cells connected to the said at least one test line at its respective cross points with the same said lines of the other of said pluralities of regular bit lines and regular word lines.

4. A field programmable device as recited in claim 1 in which adjacent, successive ones of said additional lines of said other of said pluralities of regular bit lines and regular word lines are interchanged such that the successive, interchanged additional lines are connected to said at least one test line through test memory cells of successively opposite conductivity types.

5. A field programmable device as recited in claim 1 comprising:

at least a second test line adjacent said corresponding one of said pluralities of said regular bit lines and said regular word lines and defining respective cross points with the lines of said other of said pluralities of regular bit lines and regular word lines,

test memory cells respectively connected at the said cross points of said second test line and said lines of said other of said pluralities of regular bit lines and regular word lines, and wherein said test memory cells respectively connected at the said respective cross points of said second test line are of the opposite conductivity type to the test memory cells connected to the said at least one test line at its respective cross points with the same said lines of the other of said pluralities of regular bit lines and regular word lines, and wherein adjacent, successive ones of said additional lines of said other of said pluralities of regular bit lines and regular word lines are interchanged such that the successive, interchanged additional lines are connected to said at least one test line through test memory cells of successively opposite conductivity types.

6. A field programmable device as recited in any of claims 1, 2, 3, 4, or 5 wherein each said test line is a bit test line, said corresponding one of said pluralities of regular lines is said plurality of regular bit lines, and

said other of said pluralities is said plurality of regular word lines.

7. A field programmable device as recited in any of claims 1, 2, 3, 4 or 5 wherein each said test line is a word test line,

said corresponding one of said pluralities of regular lines is said plurlaity of regular word lines, and

said other of said pluralities is said plurality of regular bit lines.