COM Port Adapter
§ Provides a simple, low-cost interface to an
RS232C COM Port for reading and writing
iButtonTM devices (DS9097E required for
programming DS198x Add-Only iButtons)
§ Adapter is powered entirely from an RS232
interface (DS9097E may require optional
auxiliary 12V supply)
§ Standard DB-9 (DSD9097) or DB-25
(DS9097E) female connector for mating the
adapter to the COM Port of a computer and
RJ-11 connector for easy attachment of a
probe such as the DS9092GT
§ DS9097E has an additional 2.1 mm male
power jack to allow for an auxiliary 12V DC
supply for programming Add-Only iButtons
Pin assignment DS9097, DB-9
TXD (3), RXD (2), DTR (4), PC-Ground (5);
all other pins not connected
Pin assignment DS9097E, DB-25
TXD (2), RXD (3), DTR (20), RTS (4), PCGround (7); all other pins not connected
Auxiliary supply should be a regulated 12V
@ 10 mA minimum, center=GND, outer
ring=V+ (Newark Electronics Stock No.
84F2081, Allied Electronics Stock No. 9289895, Stancor Model STA-300R, or
The DS9097 COM Port Adapter is a simple, low-cost passive adapter which performs RS232C (±12V)
level conversion, allowing an iButton probe to be connected to the serial port of a computer so that a nonEPROM iButton can be read and written directly. It can also read all EPROM-based iButtons. The serial
port must support a data transmission rate of 115.2 kbits/s in order to create the 1-WireTM time slots
correctly. Nearly all PCs support the required data rate and are fully compatible with the DS9097. Since
an 8-bit character (6 data bits plus start and stop bit) on the RS232 port operating at 115.2 kbits/s is used
to form a single 1-Wire time slot, the maximum effective 1-Wire transfer rate is 14.4 kbits/s (regular
speed). Details on the operation of the DS9097 including software examples are found in Application
Note 74, Section V.
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The DS9097E is an upgraded version of the DS9097 that is capable of supplying the 12 volts necessary to
program the EPROM-based iButton products (DS198x Add-Only iButtons) in addition to reading and
writing SRAM and EEPROM-based devices (DS199x, DS196x, DS197x). When combined with the
appropriate software, the DS9097E can be used in a standalone mode where all of the programming
current is supplied by the serial port itself. In this configuration, the maximum number of EPROM bits
that can be programmed simultaneously is four on a typical serial port. For higher performance, the above
mentioned 12V auxiliary supply can be plugged into the power jack on the DS9097E and with proper
software enable the serial port to program up to eight EPROM bits simultaneously.
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