iC-TW3 SENSOR SIGNAL CONDITIONER WITH
TEMPERATURE COMPENSATION AND LINE DRIVER
Rev B1, Page 12/24
1-WIRE INTERFACE
The 1-wire interface provides read and write access to coded as a short high followed by a long low. A one-bit
the register bank and to the external EEPROM. When is encoded as a long high followed by a short low.
read access is not required an infrared phototransistor
can be directly connected to the pin in order to build The modulated signal is independent of the receiver or
a cost effective wireless write-only port for in-field or the transmitted clock frequency. Since iC-TW3 uses
production programming.
a free-running oscillator it is important to implement a
robust, frequency insensitive protocol.
The communication bit stream is pulse-width modu-
lated (PWM) as shown in Figure 1. A zero-bit is en-
1- wire timing
idle
start
1
0
delay
idle
tlong
tlong
tshort
tshort
tlong
tshort
tdelay
tidle
Figure 1: Pulse width modulation bit stream
Parameter
tstart
Description
min
max
Low time start condition (Master only)
Unit time long (Master and iC-TW3)
Unit time short (Master and iC-TW3)
Delay on register read (iC-TW3 only)
1 ms
tlong
tshort + 10 µs
35 µs
400 µs
tshort
tlong - 10 µs
tdelay
35 µs
tidle
Interface idle before next access
Access was write to external EEPROM
Access was not write to external EEPROM
8 ms
3 ms
Table 7: 1-Wire interface timing
ICHAUS [ IC-HAUS GMBH ]
