JPS57185507A - Sequence controller - Google Patents

Abstract

PURPOSE:To eliminate the need for the operation of a changeover switch and to avoid forgotten operation or misoperation, by constituting so that the memory changeover can automatically be made only with the replacement of an extension memory unit. CONSTITUTION:When an extension memory unit is not extended in an extension memory unit space 18 and an extension RAM unit 19 is extended, an RAM, ROM changeover signal D goes to ''H'' level, and when a memory selection signal C is at ''H'' level, an RAM selection signal E goes to ''L'' level, and when the RAM unit 19 is extended to a basic RAM17 and the space 18, the unit 19 can simultaneously be selected. On the other hand, when an extension ROM unit 20 is extended to the space 18, since a discrimination terminal H of the RAM and ROM of the unit 20 is connected to an ''L'' level, the switching signal D goes to ''L'' level, and when the selecting signal C is at ''H'' level, an ROM selecting signal F goes to ''L'' level and the extension ROM unit 20 only is selected.