interrogation
ETIs can be interrogated via serial or
parallel format. The output select (OS)
input is used for selection of
interrogation mode.
serial elapsed time
Bytes 1 and 12 are ASCII carriage return
characters. Bytes 2 to 9 represent the
elapsed time reading and are ASCII
characters. Byte 2 is the most significant
digit. Byte 7 is always “.” and byte 11
“H” denoting units of hours. Elapsed
time measurement is suspended for
typically 300 ms during serial data
output.
serial data
(output select = 0)
Serial data transfer uses two pins, Rx
(receive data) and Tx(transmit data).
Together with a signal common, these
lines constitute a 3 wire serial
communication interface utilising a
standard non-return to zero (NRZ), data
format. Direct interface can be made
with integrated circuit UART devices.
The signals can also be level shifted to
conform to RS232 requirements.
The Rxand Txsignals must meet the
following requirements:
A High level indicates logic 1 (5V) and a
low level indicates logic 0 (0V)
The Rxinput must be a high state prior
to reception of data
A start bit, (logic 0), is
transmitted/received indicating the start
of a message
Bytes of data are transmitted/received
least significant bit first
A stop bit, (logic 1), in the 10th bit
position indicates transmission/reception
of a byte is complete
Baud rate: 9600b/s
Data bits: 8
Start bits: 1
Stop bits: 1
Parity: none
To initiate transmission of serial elapsed
time/pulse count data a unique two
character ASCII command “ET” must be
received at the Rxinput. Following
reception of a valid “ET” command the
ETI will output the elapsed time
message on the Txoutput. If an invalid
command is received an ASCII carriage
return character, (0D hex), is transmitted.
No further serial data received for a
period of 5ms.
product information
1
2
3
4
5
6
characteristics
Operating temperature range -55 to 125ºC
Storage temperature range -55 to 125ºC
Supply voltage VCC 4.5 to 5.5 Vdc
Supply voltage VAUX 4.0 to 5.5 Vdc
Supply current 1mA typical, 2mA max
Timing resolution 0.01 hours
Timing accuracy ±0.1%
Capacity (parallel mode) 104hours/106pulses
Capacity (serial mode) 105hours/107pulses
Pulse count frequency 30 Hz max
Pulse width 10ms min
VOH output logic 1 VCC -1 to VCC
VOLoutput logic 0 VSSto 0.2 x VCC
VIH input logic 1 0.8 x VCCto VCC
VILinput logic 0 VSSto 0.2 x VCC
IZhigh Z leakage current ± 10µA
byte 12345678910 11 12
character cr 00000.00 Hcr
hex 0D 30 30 30 30 30 2E 30 30 20 48 0D
“T”
max