27220 Parallax Inc, 27220 Datasheet - Page 143

• Manufacturer Part Number: 27220
• Description: BOOK STAMPWORKS
• Manufacturer: Parallax Inc

Specifications of 27220

• Accessory Type: Booklet
• Product: Microcontroller Accessories
• Lead Free Status / RoHS Status: Not applicable / Not applicable
• For Use With/related Products: StampWorks
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant, Not applicable / Not applicable

Moving Forward · Page 133
With the 74HC595, the data must be latched to the outputs after the shift process.
Latching is accomplished by briefly pulsing the Latch control line (low-high-low). This
feature prevents the 74HC595 outputs from “rippling” as new data is being shifted
into or through the device. Note that the Latch line is pulled low through a resistor;
this prevents noise from inadvertently latching invalid data to the 74HC595 outputs
while the BASIC Stamp is initializing and the I/O pins are in a high-impedance state
(floating).
Taking it Further
Being serial devices, shift registers can be cascaded, allowing the BASIC Stamp to
control dozens of 74HC595 outputs with the same three I/O pins.