ZBasic Language Reference
190
ZBasic Microcontrollers
ZX-44 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 27 would be connected directly to the
power source (same as pin 5, etc.) and pin 29 can be left open. Although not shown on this diagram, the
ground pins of the ZX-44 (pins 6, 18, 28 and 39) must be connected to the common ground of the
system.
Clock Source
The ZX-44 series devices require a clock source running at 14.7456MHz except for the ZX-44t which
required a 7.3728MHz clock. The easiest way to provide this clock source is to connect a crystal of the
correct frequency to pins 7 and 8 along with the necessary capacitors.
Recommended Crystals
Package
14.7456MHz
7.3728MHz
HC-49/US
ECS-147.4-20-4X (Digi-Key #X1102-ND)
ECS-73-20-4X (Digi-Key #X1084-ND)
HC-49/U
ECS-147.4-20-1X (Digi-Key #X1032-ND)
ECS-73-20-1X (Digi-Key #X978-ND)
Cylinder
ECS-147.4-18-9X (Digi-Key #XC-1382-ND)
The capacitor value to use depends somewhat on the layout (e.g. stray capacitance). Values in the
range of 22pF to 27pF have been used successfully in various situations.
ZX-44 Series Clock Source
If you already have a clock source at the required frequency you can feed that signal directly to pin 8. In
this case there would be no connection to pin 7.
Program Memory
Some ZX-44 series devices also require a serial EEPROM in which to store your program’s code. (The
ZX-44n, ZX-44r, ZX-44s and ZX-44t use internal Flash memory for Program Memory.) The
recommended device to use is the Atmel AT25256A (Digi-Key #AT25256A-10PI-2.7-ND). Note,
particularly, that the older part without the A suffix will not work due to its slower speed. An EEPROM
capable of operation at 7.5MHz or more is required. An alternate part is the ON Semiconductor
CAT25256LI-G (Digi-Key #ON Semiconductor CAT25256LI-G-ND).
The recommended connection to the ZX is shown below. The value of the pullup resistor is non-critical.
Anything from 4.7K to 22K should work well. Higher values will reduce power consumption somewhat.
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