| 摘要 |
A vital (i.e. fail-safe) digital control system has a keyboard encoder for generating a message based on operation instructions keyed in, the message having diverse pairs of words, a vital decoder for identifying each pair and for producing diverse output words, diverse display words and diverse display echo words, and a display for displaying a representation of the display words. The vital decoder sequentially produces diverse multi-bit checkwords based on e.g. the display words and display echo words. The checkwords are produced in response to receipt of the message words and may be based additionally on diagnostic testing routines formed before, during, and after receipt of the keyboard instructions. If sequential ones of the checkwords are complementary and agree with a predetermined multi-bit pattern, the vital decoder activates output devices in accordance with the specific keyboard instructions. <IMAGE> |
