Module stack is one of the best selling points for PCI-104 applications, greatly boosting its implementation value. But to enhance this value even further, simultaneous stacking can be achieved by controlling the switch between IDEL, CLK, REQ#, GNT and INT# signals. Diagram 1 shows a basic block diagram for INT# signals in a PCI device. The same configuration can also be apply for REQ# and GNT# signals, enabling the signals to be transferred and completing a stack.
Diagram 1. Layout for INT# signals
For these signals, a PCI device would require 4 to 1 multipexer (MUX) ICs, like the ones shown in diagram 2, to perform switching, and the output for IDSEL, CLK, REQ#, GNT# and INT# are determined by their voltage levels. This ensures that there will be no identical bus routings and eliminating resource conflicts in PCI modules when they are stacked simultaneously. The choice of ICs for controlling the switching of signals is also the major determinant for the signal’s quality. Regardless of CLK or rise times and transmission delays of the signal, they are still key factors which can’t be overlooked during the design process.
Diagram 2. Example of an controlling MUX IC
Improving the applications for PCI-104 modules through controlling MUX ICs allow sales for these modules to expand to wider user base. Building on the basic functionality of a base board, more cilent-specific requirements can therefore be fulfilled with via module stacking. This is another testimony to the professionalism of AAEON’s development team, and the expandability and applications of their products.
PS: Case study for PCI-104 product stacking
AAEON’s current PCI-104 products available for purchase include the PFM and EPIC product line as well as a wide range of PCI-104 accessory cards.