Matrix Orbital PK162-12, Техническое руководство

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2.1.8 TTL Communications
The display can be talked to at TTL (logic 0V to +5V) levels. Two modifications must be made.
Figure 13: RS-232 Selects
Jumpers 2 and 3 must be closed and 1 and 4 open.
2.1.9 I
2
C Communications
I
2
C communications runs at 100Kbps and supports up to 127 units on a single communications line. The
I
2
C data line operates on 5 volt CMOS levels.
2.1.10 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 byte’s 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 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 which 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
I
2
C address in 8bits. The 8th bit, least significant bit, LSB or Low Order Bit of the 8bit address is a read
Matrix Orbital PK162-12
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