User's Manual

© SENSITECH INC. CONFIDENTIAL – CONTROLLED DOCUMENT Page 64 of 83
A Carrier Corp. Company
PART NUMBER T82002163
REV A
Step
#
Host PC’s Action Monitor’s
Action
Action Description
1 Send 00h Rcv 00h and
discard
Wake-up Monitor by sending 1 byte
2 Rcv Protocol ID
and set-up for
correct protocol
Send Protocol ID,
low byte 01h, high
byte 00h
Acknowledge wake-up by sending back a 2
byte protocol ID of 1
3 Send 55h Rcv value and
verify it is a 55h
Send 1-byte value so monitor can verify
correct baud rate.
4 Rcv 00h byte or
timeout and start
over
Send 00h byte or
terminate login
process
If check for 55h is good, acknowledge by
sending back a 00h, otherwise terminate
login process and start over.
5 Send 4 byte login
value
Rcv 4 byte login
value and verify
Send 4-byte login value.
7Ah, 5Eh, 8Ah, A1h to verify access to the
monitor
6 Rcv 00h byte or
timeout and start
over
Send 00h byte or
terminate login
process
If check for login values is good,
acknowledge by sending back a 00h,
otherwise terminate login process and start
over.
As can be seen in Table above, the first thing to happen is the host PC initiates
communications by transmitting a 1-byte hex value of 0h to the monitor. This byte is
sent to generate an interrupt in the monitor causing it to wake up. When the monitor
is able to respond, it will reply by transmitting a 2-byte (16 bit) protocol ID hex value
of 1h back to the host computer. It does this by sending the low byte first and the
high byte second. At this point, the host PC looks at the value that it got back for the
protocol ID and determines what command protocol to use for communicating with
the monitor.
Next, the host PC sends a 1-byte hex value of 55hto the monitor. The monitor then
receives the value from the host computer and verifies whether it received a 55h or
not. If it determines that the 55h was received correctly, it will send back a 1-byte
value of 0h. If it does not receive the 55h correctly then it will terminate the login
process, return to what it was doing, and wait for the host to start over. If the host
does not retry, then the monitor will timeout after 1 minute and the monitor will
ignore any attempts to communicate with it. If the timeout occurs it will be necessary
to re-enable the communications mode and start the whole connection process over
again. The purpose of sending a 55h to the monitor is to verify the baud rate is
correct by letting the host PC know that it understood what was sent.