Datasheet

DS1977
13 of 29
Figure 7-3. MEMORY/CONTROL FUNCTION FLOW CHART
69h
Read Mem.
[w/PW]
Master TX
64-Bits [Password]
Master
TX Reset?
CRC OK?
Master RX "1"s
DS1977 sets Memory
Address = (T15:T0)
Master RX Data Byte
from Memory Address or
FFh if Password Address
Master TX
TA1 (T7:T0), TA2 (T15:T8)
Password
Accepted?
DS1977 Incre-
ments Address
Counter
End of Page?
Master RX CRC16 of
Command, Address, Data
(1
st
Pass); CRC16 of Data
(Subsequent Passes)
End of
Memory?
Master TX
Reset
N
Y
N
Y
N
Y
N
Y
N
Y
N
Y
N
Y
Decision made
by DS1977
Decision made
by Master
Master Activates
Strong Pullup
DS1977 Incre-
ments Address
Counter
Master Activates
Strong Pullup
Strong pull-
up valid?
Y
N
Master
TX Reset?
To Figure 7
4
th
Part
From Figure 7
4
th
Part
From Figure 7
2
nd
Part
To Figure 7
2
nd
Part
NOTE: The strong pullup
must be activated within
40µs after the last bit of the
password is transmitted.
Pullup duration: see t
SPUR
To continue reading the next
memory page, the strong
pullup must be activated
within 40µs after the last bit
of the CRC16 is read.
See
Note