| 摘要 |
PURPOSE:To reset automatically the control to a main program and to attain an instantaneous resetting action to a normal mode despite the breakage of the contents of a stack register, by providing a runaway preventing circuit. CONSTITUTION:A runaway preventing circuit 10 is set between an instruction decoder 7 and a stack register 6 and an address selecting circuit 5 to detect errors of the push signal PUSH and the stack signal STK delivered from the decoder 7 and suppresses the outputs of both signals. A push memory circuit stores the state of the signal PUSH and delivers a control signal to a stack signal output suppressing circuit when the signal STK is delivered together with no output of the signal PUSH to suppress the output of the signal STK. Thus the circuit 5 does not select any of input (a-d) and therefore a program counter 3 is set at '0'. Then an access is given to an address '0' by the next clock. |
