- Published in issue 12/1993 on page 16
535 card with EPROM ernulator - 2
Although there is also a signal on the ACK line of the Centronics interface in emulator mode (unless JP6 is swapped), this of little consequence because the BUSY line is held high permanently in run mode. If you use P4.0 as an input, make sure that the line does not short-circuit the output of your application when emulator mode is used. It is, therefore, recommended to drive P4.0 from an open-collector or open-drain output. This avoids the risk of short-circuits, while a pull-up resistor is not required because it is already contained in the controller.