Datasheet

as the new PIO output state arrives in its true form at the
PIO pin. To protect the transmission against data errors,
the master must repeat the PIO output data byte in its
inverted form. Only if the transmission was error-free can
the PIO status change. The actual PIO transition to the
new state occurs with a delay of t
REH
+ x from the rising
edge of the MS bit of the inverted PIO byte, as shown in
Figure 7. The value of “x” is approximately 0.2µs. To
inform the master about the successful communication
of the PIO byte, the DS28EA00 transmits a confirmation
byte with the data pattern AAh. While the MS bit of the
confirmation byte is transmitted, the DS28EA00 samples
the state of the PIO pins, as shown in Figure 6, and
sends it to the master. The master can either continue
writing more data to the PIO or issue a 1-Wire reset to
end the command.
Chain [99h]
This command allows the master to put the DS28EA00
into one of the three chain states, as shown in Figure 8.
The device powers up in the chain OFF state. To transi-
tion a DS28EA00 from one state to another, the master
must send a suitable chain control byte after the Chain
command code. Only the codes 3Ch, 5Ah, and 96h
(true form) are valid, assigned to OFF, ON, and DONE,
in this sequence. This control byte is first transmitted in
its true form and then in its inverted form. If the chain
state change was successful, the master receives AAh
confirmation bytes. If the change was not successful
(control byte transmission error, invalid control byte),
the master reads 00h bytes instead.
1-Wire Digital Thermometer with
Sequence Detect and PIO
DS28EA00
12 Maxim Integrated
t
REH
+ X
V
TH
IO
PIO
MOST SIGNIFICANT 2 BITS OF INVERTED PIO OUTPUT DATA BYTE LEAST SIGNIFICANT 2 BITS OF CONFIRMATION BYTE (AAh)
Figure 7. PIO Access Write Timing Diagram
THESE TRANSITIONS ARE PERMISSIBLE, BUT DO NOT
OCCUR DURING NORMAL OPERATION.
OFFPOWER-ON RESET (POR)
CHAIN DONE
CHAIN ON
CHAIN ON
CHAIN DONE
CHAIN OFF
OR POR
DONEON
Figure 8. Chain State Transition Diagram