Figure 5.1: Pinouts of Rocky components
Rocky was built using wire-wrap on a Vector PC/AT interface board with power and ground planes to reduce high-frequency noise problems. As mentioned in Section 4.2, a bank of 8 DIP switches was placed on the board for selection of port address and IRQ line. A small label was placed on the board next to the switches to mark each one's function.
The inputs to the auxiliary 8-bit register are connected to a 16-pin DIP socket on the board. All of the pins in one row of the socket are grounded. This allows for flexibility in connection to the socket: individual jumper wires can be inserted into the socket holes and connected to other signals on the Rocky card (such as MEMW or CS16), or a single 16-pin DIP ribbon cable header can be plugged in to connect to signals directly from CPU pins, for example. In the latter case, every other ribbon cable wire is grounded because of the grounding arrangement of the socket.
The signals REC, SRQ, and SACK were transmitted through 74LS14 Schmitt inverters with hysteresis to reduce false triggering because of noise. Several other GAL outputs with large fan-out were inverted to reduce loading for a faster rise and fall time. Decoupling capacitors were placed near several of the chips power supply leads.
The 40 pin ribbon cable connectors were wired with half of the pins grounded and with pinouts compatible with the 40 pin Pod headers of the HP 1650 Logic Analyzer. This allows the logic analyzer to be plugged directly into Rocky for testing.
For when Bullwinkle is not connected to generate stall requests, a wire was connected to one of the SRQ pins so that by grounding it a manual Stall Request could be generated. This method was used to test the interrupt handler software and verify correct stall and resume operation.