User's Manual

© SENSITECH INC. CONFIDENTIAL – CONTROLLED DOCUMENT Page 55 of 83
A Carrier Corp. Company
PART NUMBER T82002163
REV A
TempTale Mini
During normal monitor operation, communications mode is disabled. In order to enable the
communications mode by means of the communications enable pin on the RS232 connector located
inside the monitor. This pin must be held during the entire communications session. The monitor
communicates via a standard RS232, 9600 baud rate, 8 bit, No Parity, 2 Stop bit protocol. (9600,8,N,2)
Once the monitor has entered communications mode, the host PC is responsible for establishing a
connection with the monitor. If the host PC does not establish a connection within one minute’s time,
the microcontroller within the monitor will disable communications mode thus terminating
communications. If this occurs, it will be necessary to re-enable the communications mode by re-
triggering the communications enable line.
To establish a connection with the monitor, the host PC must send a sequence of
Bytes to the monitor and receive the correct responses back from the monitor. This sequence is designed to
give the monitor time to wake-up and allow the host to log in. If any of the bytes are sent or received
incorrectly or at the wrong time during the connection attempt, both the host and monitor should
assume bad communications and return to their previous states. The following table shows the steps
that are taken to connect to the monitor:
Table 1
Step
#
Host PC’s Action Monitor’s
Action
Action Description
1 Toggle
Communications
Enable Line
(DTR)
Detect Com Line
toggle and enter in
Comm. Mode
Wake-up Monitor via RS232 line toggle
2 Send 00h Rcv 00h and
Send Product ID of
02h to host
Host send 00h
Monitor replies by sending 2 byte Product
ID of 02h, low byte 02h, high byte 00h,
LSB first
3 Rcv ID and set-up for
correct protocol
Send Next Command
Rcv command
from host and act
accordingly
Host determines monitor type via ID value
and sends next action command.
As can be seen in Table 2 above, the first thing to happen is the monitor enters communications mode via a
change in state in the “detect” line from the RS232 connector. (“Detect” = Pin 4 (DTE Ready) of the
DB9 connector)
The host PC initiates communications by transmitting a 1-byte hex value of 0h to the monitor.
When the monitor is able to respond, it will reply by transmitting a 2-byte (16 bit) protocol ID hex value of
2h back to the host computer. It does this by sending the low byte first and the high byte second.
The host PC then looks at the value that it got back for the protocol ID and determines what command
protocol to use for communicating with the monitor.
Once the host PC has successfully logged in and has established a connection with the monitor. The host
PC may now send predefined commands to the monitor, which allows it to do things such as, configure
the monitor or download the data. The command protocol and a list of the commands with their
definitions are described in a later section. It is also important to note that once a connection has been
established, a 3-minute timeout timer is established within the monitor in place of the 1-minute timeout