LCD0821 rev 2
11
The module is supplied with jumpers J1 and J2 installed, which gives a RS-232 baud rate of 19200 and an
I
2
C address of 0x5C.
RS-232 port: J0, J1, J2 - control baud rate. RS-232 format is 8N1 (8 bits, no parity, one stop bit)
I²C port: J0, J1, J2, J3 - sets slave peripheral address
Baud Rate
Slave Address
J3
J2
J1
J0
50H
out out out out
1200
52H
out out out in
54H out
out
in
out
2400
56H out
out
in
in
58H
out in out out
9600
5AH
out in out in
5CH out
in
in
out
19200
5EH out
in
in
in
60H in
out
out
out
1200
62H in
out
out
in
64H
in out in out
2400
66H
in out in in
68H in
in
out
out
9600
6AH in
in
out
in
6CH
in in in out
19200
6EH
in in in in
2.1.6 I
2
C Communications
I²C communications runs at 100 kBps and supports up to 16 units on a single communications line. The
I2C data line operates on 5 volt CMOS levels.
The idea of ACK is to indicate when the data has been received correctly. ACK does not indicate data
incorrectly received. ACK simply fails to indicate when data is correctly received. Clearly, this is of limited
usefulness and even less so with Matrix Orbital modules. Matrix orbital modules are not capable of failing
to acknowledge an incorrectly received byte in response to that bytes transition. They are only capable of
failing to acknowledge the bytes following the byte, which was not received. To fully understand the
reasons for this one needs to understand something about how a Matrix Orbital module processes data.
Basically the reason why a Matrix Orbital module might fail to receive a byte correctly is that it was unable
to process the byte previous before the failed byte was transmitted. Because the module cannot possibly
know that it would be unable to store the byte before the next byte was received it cannot know to not ACK.
The reason for this situation in deference to situations you might be familiar with (i.e. memory chips, etc…)
is that the Matrix Orbital module employs a microprocessor to perform these data storage functions. A
memory chip takes care of these things entirely with in hardware subsystems that operate at the same speed
as the transmission themselves.
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