Subject: KPC3 512k upgrade From: Warren Stone KPC-3 512K upgrade Kantronics KPC-3 512k upgrade. It is possible to expand the KPC-3 memory quite easily with a 128K chip. Simply plug in the chip and you can get five nodes and a 101000 byte mailbox. According to the the Kantronics KPC-3 manual, the unit is expandable to 512K. Unfortunately, no 512K static RAM is currently being manufactured at prices easily affordable. By simply using the two extra address lines Kantronics has built into the KPC-3 along with a few 128K chips and a decoder it is possible to build 512K into the TNC giving five nodes and a huge 491000 byte mailbox! Kantronics has made available two extra address lines which will be used by the new expanded RAM. These are used, along with a 74HC139 decoder IC and four 128K static RAMs to build all 512K into the TNC. Using this combination will allow five nodes, and a huge 491000 byte mailbox! I used four KM681000ALP-8 128K static RAMs. If you use a different type, plug in a single RAM IC to verify it will work. When inactive, the data lines of the memory ICs are in a high impedance state. They are neither logic 1 nor logic 0. Address lines are high impedance inputs. All remaining pins are either for power or left unused. Except for the individual chip enable lines, all lines may be bridged. Only when selected will the data lines be active for reading or writing information. The 74HC139 is a 2 to 4 line decoder. I am using the original enable line of U9 at pin 22 to control its output. The extra two address lines select which of the four output lines will be active when the memory is addressed. The 74HC139 will drive one of the four memory ICs. Begin by placing all four memory ICs in a stack. Solder all common pins of the four ICs except pin 22. Use needle nose pliers to bend each pin 22 at right angles to its existing position so the four pins stick out to the side of the stack. The socket for U9 must be removed to allow the cover to fit when the four ICs are installed. Carefully desolder it and clean all the pin holes. Solder the four ICs into the space used by U9, observing the correct position. Place the 74HC139 on the side of the memory stack with the pins sticking out. I glued it upside down to the top of the microprocessor, U4. Apply +5V to pins 13, 14, 15, and 16. 5V is available at pin 32 of U9. Connect pin 8 to ground at pin 16 of U9. Address line A17 connects to pin 2 of the 74HC139. It is available at J6, pad 2. This is the closest pad to U9, next to Q1. Desolder the pad and place the wire through the board. Do not change the trace at J6 between the center pad and position 1. Address line A18 comes from pin 1 of U9. It is available at a hole through the board on the other side of Q1 from J6. Follow the trace on top of the board from pin 1 and you will see it. Desolder the hole and put a wire through. Connect it to pin 3 of the 74HC139. Place a wire from the empty hole for pin 22 of U9 to pin 1 of the 74HC139. Finally, connect pins 4, 5, 6, and 7 to each of the four pins of the memory stack. Refer to Figure 1 for details of wiring the 74HC139. When everything is wired up, put the jumper across J7 and perform a hard reset. With the terminal set to 1200 baud, the TNC will report 512K available memory! Remove the jumper and reprogram all the parameters. Even with CD SOFTWARE and LEDS ON current in my KPC3 is still less than 15mA. As an extra note, this technique can be used to increase the memory in the KPC9612 or KAM Plus as well. There will have to be minor changes made to the connection points to suit the particular TNC, but the overall method remains the same. 74HC139 =DA=C4=C4=C4=C4=C4=C4=C4=C4=C4=BF U9, pin 22 pc board connection =C4=C4=C4=C4=C4=C4=C4=C4=B41 =DF 16=C3=C4= =C4=C4=C2=C4=C4=C4 +5V =B3 =B3 =B3 =B3 =B3 =B3 J6, pad 2 (A17) =C4=C4=C4=C4=C4=C4=C4=C4=B42 15=C3=C4= =C4=C4=B4 =B3 =B3 =B3 =B3 =B3 =B3 U9, pin 1 (A18) =C4=C4=C4=C4=C4=C4=C4=C4=B43 14=C3=C4= =C4=C4=B4 =B3 =B3 =B3 =B3 =B3 =B3 Pin 22 top 128K IC =C4=C4=C4=C4=C4=C4=C4=C4=B44 13=C3=C4= =C4=C4=D9 =B3 =B3 =B3 =B3 Pin 22 second 128K IC =C4=C4=C4=C4=C4=C4=C4=C4=B45 12=C3=C4 n= /c =B3 =B3 =B3 =B3 Pin 22 third 128K IC =C4=C4=C4=C4=C4=C4=C4=C4=B46 11=C3=C4 n= /c =B3 =B3 =B3 =B3 Pin 22 bottom 128K IC =C4=C4=C4=C4=C4=C4=C4=C4=B47 10=C3=C4 n= /c =B3 =B3 =B3 =B3 =DA=C4=C4=B48 9=C3=C4 n/c =B3 =C0=C4=C4=C4=C4=C4=C4=C4=C4=C4=D9 =DA=C4=C5=C4=BF Figure 1. 74HC139 wiring diagram. Send a message via packet to VO1KS @ VE1BBS.NS.CAN.NA if you have further questions or comments. Email ar772@chebucto.ns.ca 73 de Warren VO1KS