This article is a continuation of the series which began in the October 1989 issue of QZX. The purpose is to explain the function of the SCL logic chip in the ZX and TS1000 series of Sinclair computers. This chip is a custom chip designed particularly for our computers. The previous articles gave some background on the chip, provided a functional diagram, and listed 17 separate functions performed by the chip. These and succeeding articles discuss these functions individually and provide an equivalent circuit diagram for the function. These circuit diagrams are only the equivalent of the actual circuits inside the chip because nothing is known about the real connections inside, but the circuits given here will perform the function of the real circuit. For a list of these 17 functions see the October issue of QZX.
Last month we looked at the last of the circuits when the video, tape and select circuits were discussed. This month concludes the series with a discussion of some of the parameters used by the SCL and a few notes on the timing of some of the signals. For a discussion cf the timing signals and a timing diagram, see the December (1989) issue of QZX.