27220 Parallax Inc, 27220 Datasheet - Page 152

• 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

Behind the Scenes
This program is very similar to 74HC595 cascading in that the serial output from one
shift register is fed into the serial input of the next device up the chain.
important to note that cascaded stages are connected using the non-inverted output;
only the stage connected directly to the BASIC Stamp uses the inverted output (all
data passing through will be inverted here).
In the program the Get_165x2 subroutine has been updated to accommodate the
second 74HC165. Since a Word variable was defined for the external inputs, the bit
modifier is used with SHIFTIN; this allows all sixteen bits to be collected at one
time. The bit modifier is only required when the number of bits differs from eight
(default bit count).
We could also define separate Byte variables for each device. The code fragment
below shows how we could handle this situation:
In this example, the variable called switches would be loaded with the data from
the first shift register in the chain (i.e., the device connected to the BASIC Stamp).
Get_165x2:
PULSOUT Load, 5
SHIFTIN SerData, Clock, MSBPRE, [switches, buttons]
RETURN
' load inputs
It is