METHOD FOR REQUESTING SERVICE BY A DEVICE WHICH GENERATES A SERVICE REQUEST SIGNAL SUCCESSIVELY UNITL IT IS SERVICED

A method for requesting service by a device coupled to a host computer through a communication medium. The host computer sets a service request bit of the device to a first logical value to allow the device to produce a service request signal if the device requires servicing. The device determines that it requires servicing and the device sets an internal flag bit to a first logical value to indicate that the device requires servicing. The device monitors a command from the host computer to see if the command is addressed to the device. If the command is not addressed to the device and if the service request bit is set to a first logical value, then the device generates a service request signal on the medium after the command by holding the communication medium low for a first period of time. If the command is addressed to the device, if the device determines that the command is not a command that services the device, and if the service request bit is set to the first logical value, then the device generates a service request signal on the medium after the command by holding the medium low for the first period of time and performs the command. If the command is addressed to the device, if the device determines that the command is not a command that services the device, and if the service request bit is not set to the first logical value, the device performs the command without generating the service request signal. The steps including and following the step of the device monitoring a command from the host computer are repeated until the device receives a command addressed to the device that services the device.