139 of 158
133 Appendix C - ZX-40 Series Hardware Reference The ZX-40 devices are the 40-pin DIP package versions of the Atmel AVR ATmega32, ATmega644 or ATmega644P microcontrollers that have been programmed with the ZX control firmware. They offer the same capabilities as the ZX-24 series plus access to 7 additional I/O pins. In order to use the ZX-40 series devices you must add several additional components as described below. In each of the diagrams presented below, only a portion of the device’s 40 pins is shown. Those that are not germane to the circuit being discussed are omitted for clarity. C.1 ZX-40 Series Specifications The electrical specifications of the ZX-40, ZX-40a, ZX-40p are exactly those of the underlying ATmega microcontrollers. Rather than reproducing them here the reader is directed to the datasheet published by Atmel. It can be obtained from the Atmel website |http://www.atmel.com or from the ZBasic website | http://www.zbasic.net. C.2 ZX-40 Series Required External Components Power Source The ZX-40 series devices need a regulated voltage source capable of providing at least 200mA of current. The voltage typically used is 5 volts but the device will operate between 4.5 volts and 5.5 volts. A recommended circuit is shown below. A suitable heatsink will probably be required in most cases to keep the regulator IC below its maximum operating temperature. Consult the regulator datasheet for more information. ZX-40 Series Power Source If you do not plan to use the Analog-to-Digital converter channels you can eliminate the inductor and the two capacitors on the right side of the diagram. In this case, pin 30 would be connected directly to the power source (as are pins 10 and 30) and pin 32 can be left open. Although not shown on this diagram, the ground pins of the ZX-40 (pins 11 and 31) must be connected to the common ground of the system. Clock Source The ZX-40 series devices require a clock source running at 14.7456MHz. The easiest way to provide this clock source is to connect a crystal of that frequency to pins 12 and 13 along with the necessary capacitors. The recommended crystal to use is ECS-147.4-20-4 (Digi-Key #X175-ND). An alternate crystal in a slightly larger package is ECS-147.4-20-1 (Digi-Key #X142-ND). The capacitor value to use depends