The purpose of the 9000A-9900 Interface Pod, hereafter referred to as the pod, is to interface any 9000 Series Micro System Troubleshooter to a piece of equipment employing a 9900 microprocessor. The 9000 Series Micro System Troubleshooters are designed to service printed circuit boards, instruments and systems employing bus-oriented microprocessors. While the architecture of the troubleshooter main frame is general in nature and is designed to accomodate processors with up to 32 address lines and 32 data lines, the interface pod adapts the general purpose architecture of the 9000 Series to a specific microprocessor, or microprocessor family. The interface pod adapts the 9000 Series to microprocessor-specific functions such as pin layout, status/control functions, interrupt handling, timing, size of memory space, and size of I/O space. 1-2. DESCRIPTION OF INTERFACE POD The pod consists of a pair of printed circuit board assemblies, chassis-mounted within a break-resistant case. A shielded 24-conductor cable connects the printed circuit boards to the troubleshooter; a shielded ribbon cable and connector provide connection to the unit under test, hereafter referred to as the UUT. Figure 1-1 shows the relationship of the pod to the troubleshooter and to the UUT. Connection from the pod to the troubleshooter is via a front-mounted 25- pin connector. Connection to the UUT is made by plugging the ribbon cable plug directly into the microprocessor socket. The UUT microprocessor socket gives the troubleshooter direct access to all system components which normally communicate with the microprocessor. The pod contains a 9900 microprocessor and the supporting hardware and control software required to: • Perform handshaking with the troubleshooter 1-1 9900 • Receive and execute commands from the troubleshooter • Report UUT status to the troubleshooter • Emulate the UUT microprocessor The pod is powered by the troubleshooter, but is clocked by the UUT clock signals. Using the UUT clock signals allows the troubleshooter and pod to operate at the designed operating speed of the UUT. Logic level detection circuits are provided on each line to the UUT. These circuits allow detection of bus shorts, stuck-high or stuck-low conditions, and any bus drive conflict (two or more drivers attempting to drive thesame bus line). Over-voltage protection circuits are also provided on each line to the UUT. These circuits guard against pod damage which could result from: • Incorrectly inserting the ribbon cable plug in the UUT microprocessor socket. • UUT faults which place potentially damaging voltages on the UUT microprocessor socket. The over-voltage protection circuits guard against voltages of+12 to -7 volts on any one pin. Multiple faults, especially of long duration, may cause pod damage. A power level sensing circuit constantly monitors the voltage level of the UUT power supplies. If UUT power rises above or drops below an acceptable level, the pod notifies the troubleshooter of the power fail condition. A self test socket provided on the pod enables the troubleshooter to check pod operation. The self test socket is a 64-pin zero-insertion force type connector. The ribbon cable plug must be connected to the self test socket during self test operation. The ribbon cable plug should also be inserted into this socket when the pod is not in use to provide protection for the plug.