Parallax BASIC Stamp 2e - Page 204

OWIN - BASIC Stamp Command Reference
Page 202 • BASIC Stamp Programming Manual 2.0b • www.parallaxinc.com
Command Value (in Hex) Action
Read ROM $33
Reads the 64
-bit ID of the 1-wire device. This command
can only be used if there is a single 1
-wire device on the
line.
Match ROM $55
This command, followed by a 64
-bit ID, allows the BASIC
Stamp to address a specific 1
-wire device.
Skip ROM $CC
Address a 1
-wire device without its 64-bit ID. This
command can only be used if there is a single 1
-wire
device on the line.
Search ROM $F0
Reads the 64
-bit IDs of all the 1-
wire devices on the line. A
process of elimination is used to distinguish each unique
device.
The third part, the Memory Function Command, allows the BASIC Stamp
to address specific memory locations, or features, of the 1-wire device.
Refer to the 1-wire device's data sheet for a list of the available Memory
Function Commands.
Finally, the Transaction/Data section is used to read or write data to the
1-wire device. The OWIN command will read data at this point in the
transaction. A read is accomplished by generating a brief low-pulse and
sampling the line within 15
µs of the falling edge of the pulse. This is
called a "Read Slot." Figure 5.19 shows typical Read Slots performed by
the BASIC Stamp. See the OWOUT command for information on Write
Slots.
BASIC Stamp’s
Read “0” Slot
Apx. 72 sµ
Recovery Period
Apx 8 s
µ
+5 (vdd)
0 (vss)
BASIC Stamp’s
Read “1” Slot
Apx. 72 sµ
driven by BASIC Stamp
time when BASIC Stamp samples line (apx 1 - 10 s)
µ
Apx 4 s
µ
Apx 4 s
µ
driven by 1-wire device or pulled-up by 5 k resister Ω
Table 5.47: 1-wire ROM Function
Commands.
Figure 5.19: Example Read Slot.