Matrix Orbital LK162-12 Legacy - Manual (Page 14)

LK162-12 rev 4 14
1 2 3 4
Pin 1 Vdc
Pin 2 Tx
Pin 3 Rx
Pin 4 Ground
2.1.6 TTL Communications
The LCD2041 can be talked to at TTL (logic 0V to +5V) levels. Two modifications have to be made.
Jumpers 2 and 3 have to be closed and 1 and 4 open.
2.1.7 I²C 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 wa s 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.
The LK404-55 uses a standard Phillips 7bit address as defined by Phillips. How ever, we at Matrix Orbital
specify I2C address in 8bits. The 8
th bit, least significant bit (LSB or Low Order Bit) of the 8bit address is
read/write bit. If we take a standard Phillips 7bit address of 45hex this would be in binary 1000101. This is
7bits. If one adds the read write bit to this 7bit address and you assume that you are writing one gets