Floppy disk controller interface for suppressing false verify cycle

Abstract

A system includes a system bus having data lines, an acknowledge line, an enable line, and a control line, a data storage device, a controller circuit, and an arrangement coupling the system bus, controller circuit and data storage device. The system bus can carry out a data transfer cycle in which the acknowledge, enable and control lines are actuated and the controller obtains and checks data from the data storage device and supplies it to data lines of the bus, and a verify cycle in which the acknowledge and enable lines are actuated and the control line is deactuated and the controller obtains and checks data from the storage device but does not supply it to the bus. The controller circuit is capable of operating in different modes, in one of which it forcibly sets a false error indication in response to the verify cycle. In response to the acknowledge line and enable line being simultaneously actuated while the control line remains deactuated throughout a cycle, an arrangement supplies a special signal to the controller circuit so that the controller circuit interprets the cycle as a data transfer cycle and does not set a false error indication.