Parallax BASIC Stamp 2e Programming Manual page 317

A SHIFTOUT
SIMPLE EXAMPLE
C
ONTROLLING THE NUMBER OF BITS
.
TRANSMITTED
SHIFTOUT
ACCEPTS VARIABLES AND
O D
EXPRESSIONS FOR UTPUT
B .
ITS ARGUMENTS
5: BASIC Stamp Command Reference – SHIFTOUT
Here is a simple example:
.
SHIFTOUT 0, 1, MSBFIRST, [ 250 ]
Here, the SHIFTOUT command will write to I/O pin 0 (the Dpin) and will
generate a clock signal on I/O 1 (the Cpin). The SHIFTOUT command will
generate eight clock pulses while writing each bit (of the 8-bit value 250)
onto the data pin (Dpin). In this case, it will start with the most significant
bit first as indicated by the Mode value of MSBFIRST.
By default, SHIFTOUT transmits eight bits, but you can set it to shift any
number of bits from 1 to 16 with the Bits argument. For example:
SHIFTOUT 0, 1, MSBFIRST, [ 250 \4 ]
Will only output the lowest 4 bits (%0000 in this case).
Some devices require more than 16 bits. To solve this, you can use a single
SHIFTOUT command with multiple values. Each value can be assigned a
particular number of bits with the Bits argument. As in:
SHIFTOUT 0, 1, MSBFIRST, [ 250\4 , 1045\16]
The above code will first shift out four bits of the number 250 (%1111) and
then 16 bits of the number 1045 (%0000010000010101). The two values
together make up a 20 bit value.
In the examples above, specific numbers were entered as the data to
ATA AND
transmit, but, of course, the SHIFTOUT command will accept variables
and expressions for the OutputData and even for the Bits argument.
BASIC Stamp Programming Manual 2.0c • www.parallaxinc.com • Page 315