28129 Parallax Inc, 28129 Datasheet - Page 40

• Manufacturer Part Number: 28129
• Description: TEXT BASIC ANALOG & DIGITAL
• Manufacturer: Parallax Inc
• Type: Programmingr

Specifications of 28129

• Style: Book
• Title: Basic Analog and Digital
• Contents: Basic Analog and Digital Text
• Product: Microcontroller Accessories
• Lead Free Status / RoHS Status: Not applicable / Not applicable

Parallel and Serial Transmission
Program Listing 2.1 repeats the entire check and report on the pushbutton states routine
over and over again. Because the BASIC Stamp checks for input over and over again
without waiting for some kind of signal that the data is ready, we are sending the binary
numbers to the BASIC Stamp asynchronously.
We are also sending the binary bits across two separate data lines at the same time. This
means we are sending our data bits to the BASIC Stamp in parallel
The BASIC Stamp has a 16 I/O pins. We could actually send a word-size binary number
to the BASIC Stamp in parallel. The problem is that we wouldn't have any pins left for
outgoing signals or other input data. When dealing with larger binary numbers, sending
serial
Stamp I/O pins used to receive data.
When sending serial data, there has to be some way of letting the BASIC Stamp know
when each new bit is ready. The BASIC Stamp has built-in functions for sending
asynchronous as well as synchronous serial data.
In this next example, the same two pushbuttons are used to send the BASIC Stamp a
nibble (4-bits) of serial, synchronous data. The result is displayed in the Debug Terminal.
data instead of parallel data can be useful because it reduces the number of BASIC
Asynchronous means not synchronized. In the case of our binary keypad, it means that
we change the binary values whenever we want to without waiting for permission from the
BASIC Stamp to do so. Likewise, the BASIC Stamp checks the signals at P0 and P1 as fast
as it can without waiting for a signal from us that says the data is ready to be checked.
Parallel means the data bits are sent across more than one data line at the same time. We
just finished using the pushbuttons to send two parallel bits.
Serial: Instead of sending data in parallel along multiple data lines, a single data line can be
used and the data bits can be sent one after another.
Synchronous: Sending data synchronously means we are sending the data in time
coordinated manner (in sync). Technically, it means that the sender and receiver of the data
bits do so according to signals from the same clock
.