DS2408 Maxim, DS2408 Datasheet - Page 37

• Manufacturer Part Number: DS2408
• Description: The DS2408 is an 8-channel, programmable I/O 1-Wire® chip
• Manufacturer: Maxim

After all DS2408s are initialized, perform the search process below as an endless loop:
Note 1: For a full description of the Search Algorithm see Application Note 187.
Step 4
Step 5
MASTER MODE
(—)
(—)
TX
TX
RX
RX
RX
RX
RX
RX
RX
TX
TX
TX
TX
TX
TX
TX
TX
DATA (LSB FIRST)
<2 bytes CRC16>
<8 data bytes>
(Presence)
(Presence)
<2 bits>
<1 bits>
<2 bits>
<1 bits>
(Reset)
(Reset)
ECh
AAh
A5h
(—)
F0h
88h
00h
(—)
C3
37 of 39
Reset pulse
Presence pulse
Issue Conditional Search ROM command
Read 2 bits; if both bits are 1, no push button
has been pressed; in this case return to Step
4. If the bit pattern is 01 or 10 or 00, a push
button has been pressed; in this case
continue with Step 5.
Identify and select the LS bit of the ROM ID
of the DS2408 that has responded to the
Conditional Search.
Read 2 bits; this relates to the next bit of the
ROM ID of the participating device(s).
Identify and select the next bit of the ROM ID
of the DS2408 that has responded to the
Conditional Search.
Repeat the previous 2 steps until one device
has been identified and accessed. (see Note
1)
Issue Read PIO Registers command
TA1, target address = 88h
TA2, target address = 0000h
Read register page; the data in the Activity
Latch State Register tells which button has
been pressed.
Read CRC16 and verify correct data
transmission.
Reset pulse
Presence pulse
Issue Resume command
Issue Reset Activity Latch command
Read for verification (AAh = success)
Now, as the device and push button are
identified and the Activity Latch is cleared,
continue at Step 4.
COMMENTS
DS2408