| 摘要 |
<p>Coding circuitry (34), for use for example in selecting cells of a cell array in a digital-to-analog converter, produces first and second sets of thermometer-coded output signals in dependence upon a binary input signal. As the input signal increases progressively in value from a first value to a second value, the first-set output signals (COLA) are activated in a predetermined sequence and the second-set output signals (COLB) are deactivated in a predetermined sequence. As the input signal increases progressively in value from the second value to a third value, the first-set output signals are deactivated in a predetermined sequence and the second-set output signals are activated in a predetermined sequence. Such coding circuitry reduces the numbers of output signals that change in response to changes in the input-signal value. ÄFIGURE 6Ü In another embodiment (Figure 12) the coding circuitry includes respective row, column and depth decoders (58, 56, 54). The row decoder receives the two most significant bits S4 and S5 of a binary input word and derives therefrom a set of thermometer-coded row selection signals (ROW0-2). The column decoder receives the two middle-order bits S2 and S3 of the binary input word and derives therefrom at least one set of thermometer-coded column selection signals (COLA0-2,COLB0-2). The depth decoder receives the two least-significant bits S0 and S1 of the binary input word and derives therefrom at least one set of thermometer-coded depth selection signals (DEPA0-2,DEPB0-2). Such coding circuitry can enable selection of elements from amongst a large array of elements using only a small number of thermometer-coded signals. <IMAGE></p> |
