Rainbow Electronics DS2432 - Manual (Page 30)

PRELIMINARY DS2432
30 of 30
AC ELECTRICAL CHARACTERISTICS
OVERDRIVE SPEED
(V
PUP
=2.8V to 5.25V; -40°C to +85°C)
PARAMETER SYMBOL MIN TYP MAX UNITS NOTES
Time Slot t
SLOT
6 16 µs
Write 1 Low Time t
LOW1
1 2 µs
Write 0 Low Time t
LOW0
6 16 µs
Read Low Time t
LOWR
1 2 µs
Read Data Valid t
RDV
2 µs 10
Release Time t
RELEASE
0 1.5 4 µs
Read Data Setup t
SU
1 µs 4
Recovery Time t
REC
1 µs
Reset High Time t
RSTH
48 µs
Reset Low Time t
RSTL
48 80 µs
Presence Detect High t
PDHIGH
2 6 µs
Presence Detect Low t
PDLOW
8 24 µs
Programming Time t
PROG
10 ms
SHA Computation Time t
CSHA
1.0 2.0 ms 9
NOTES:
1. All voltages are referenced to ground.
2. V
PUP
= external pull-up voltage.
3. Input load is to ground.
4. Read data setup time refers to the time the host must pull the 1-Wire bus low to read a bit. Data is
guaranteed to be valid within 1 µs of this falling edge.
5. Capacitance on the data pin could be 800 pF when power is first applied. If a 5 k
Ω
resistor is used to
pull up the data line to V
PUP
, 5 µs after power has been applied the parasite capacitance will not affect
normal communications.
6. The reset low time (t
RSTL
) should be restricted to a maximum of 960 µs, to allow interrupt signaling,
otherwise, it could mask or conceal interrupt pulses.
7. V
IH
is a function of the external pull-up resistor and V
PUP
.
8. Under certain low voltage conditions V
ILMAX
may have to be reduced to as much as 0.5V to always
guarantee a Presence Pulse. V
IL
is a function of V
PUP
and the reset low time.
9. During write operations to the EEPROM and during the computation of Message Authentication
Codes (MAC) the voltage on the 1-Wire bus must not fall below 2.8V. The computation of a MAC
takes maximum 2.0 ms. Copying scratchpad data to the EEPROM takes max. 10 ms.
10. The optimal sampling point for the master is as close as possible to the end time of the t
RDV
period
without exceeding t
RDV
. For the case of a Read-one time slot, this maximizes the amount of time for
the pull-up resistor to recover the line to a high level. For a Read-zero time slot it ensures that a read
will occur before the fastest 1-Wire device releases the line (t
RELEASE
= 0).