DS1985 Maxim, DS1985 Datasheet - Page 20

• Manufacturer Part Number: DS1985
• Description: The DS1985 16Kb Add-Only iButton is a rugged read/write data carrier that identifies and stores relevant information about the product or person to which it is attached
• Manufacturer: Maxim

(Figure 11) should be applied for 480 s, after which the bus master returns the data line to an idle high
state controlled by the pullup resistor. Note that due to the high voltage programming requirements for
any 1-Wire EPROM device, it is not possible to multidrop non-EPROM based 1-Wire devices with the
DS1985 during programming. An internal diode within the non-EPROM based 1-Wire devices will
attempt to clamp the data line at approximately 8 volts and could potentially damage these devices.
INITIALIZATION PROCEDURE “RESET AND PRESENCE PULSES” Figure 9
 In order not to mask interrupt signaling by other devices on the 1-Wire bus, t
READ/WRITE TIMING DIAGRAM Figure 10
Write-1 Time Slot
be less than 960 s.
RESISTOR
MASTER
DS1985
RESISTOR
MASTER
480 s  t
480 s  t
15 s  t
60 s  t
60 s  t
1 s  t
1 s  t
LOW1
REC
PDH
PDL
SLOT
RSTL
RSTH
< 
20 of 26
< 240 s
< 60 s
< 15 s
< 120 s
<  *
<  (includes recovery time)
RSTL
+ t
R
should always