C communications – Matrix Orbital VK204-25 Legacy User Manual
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Table 5: Serial Baud Rates
Baud Rate Slave Address
J3
J2
J1
J0
1200
50H
out
out
out
out
52H
out
out
out
in
2400
54H
out
out
in
out
56H
out
out
in
in
9600
58H
out
in
out
out
5AH
out
in
out
in
19200
5CH
out
in
in
out
5EH
out
in
in
in
1200
60H
in
out
out
out
62H
in
out
out
in
2400
64H
in
out
in
out
66H
in
out
in
in
9600
68H
in
in
out
out
6AH
in
in
out
in
19200
6CH
in
in
in
out
6EH
in
in
in
in
2.2 I
2
C Communications
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C communications runs at 100 Kbps and supports up to 16 units on a single communications line. The
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C data line operates on 5 volt CMOS levels.
2.2.1 ACK
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 one might be familiar with (i.e., memory chips, etc) is that the Matrix
Orbital module employs a micro-processor to perform these data storage functions. A memory chip takes
care of these things entirely within hardware subsystems that operate at the same speed as the transmission
themselves.
The display uses a standard Phillips 7bit address as defined by Phillips. However, Matrix Orbital specifies
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C address in 8bits. The 8th bit, least significant bit (LSB or Low Order Bit) of the 8bit address is read
Matrix Orbital
VK204-25
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