Designing Embedded Internet Devices
Figure 6-38: Detail of the parallel IO selection circuitry
U4 is a dual 1-of-4 decoder14. One of the decoders handles selecting circuitry for reads and one handles selecting circuitry for the writes. U3 is an OR gate whose output will be logic “1” unless both inputs are “0.” This means that the second decoder (U4:B) will only be selected if both /SEL0 and /WR are low. Decoder U4:A is selected by /PSEN, which is active during memory reads. Table 6-8 illustrates the memory map for reading and writing to the parallel port on the E20.
The LCD interface from earlier versions
Earlier versions of the E20 socket board had unpopulated component space for an LCD interface. While this feature has been removed from the current revision of the E20, the concept for the LCD interface still works. You simply have to implement the same circuitry on a breadboard. This is discussed extensively in Chapter 8.
Other TINI socket accessories
A number of companies produce accessories for TINI. Here is a quick summary of some of them.
Vinculum Technologies Group
Vinculum Technologies Group15 produces several accessories. They have a product called the TINI ProtoAdaptor, which features a SIMM socket, power connector, DTR jumper, DB-9 serial connector, and RJ-45 Ethernet connector on a narrow circuitboard strip that has tall wire wrap pins (connecting to the TINI signals) on the board. This board can be inserted into a solderless breadboard for experimentation, or it can be used in conjunction with another of their products, the TINI Nexus. The TINI Nexus has a connector that mates to the long pins on the TINI Proto Adaptor, as well as an additional SIMM socket, and board footprints for a variety of connectors and components. They also produce a product called the ProtoModule, which is a small SIMM circuit board that has no components on it. What it does have is an array of holes and a labeled SIMM edge card that mates with the SIMM sockets used for TINI. You can use this board to make your own hardware for mating with a TINI.
A company called Systronix produces several TINI-related products, including the TILT, (TINI Initial Learning Tool), the STEP (Systronix TINI Engineering Platform), and the STEP+. These comprise a tiered family of socket boards, ranging from the basic to the sophisticated. Complete details on all their products can be found on their website16.
Additional products and vendors
A host of other products are available for TINI, with a variety of companies making them. A good place to keep tabs on new developments is the TINI website partner marketplace, which lists information on products available for the TINI stick17.