Datasheet

DS_INLC10AQ Revision 1.0_B

Inova Semiconductors Confidential

Page 14 of 35

4.1.2 Half-Duplex Communication

The communication operates in a strict master slave manner. I.e. the microcontroller as the master always

initiates the communication. Depending on the type of command the LED devices may send a response

(read access) or just silently execute the command (write access). There are three basic types of commands

which are described in the following.

4.1.3 Basic Frame Format

Commands and the response to commands are transmitted with serial frames. A serial frame always

consists of a frame_sync section, followed by a frequency_sync section, followed by a run length coded

command section and finally terminated with an optional CRC section. The command and the CRC sections

differ in length between downstream and upstream frames.

The bit encoding ensures a maximum number of adjacent zeros of 4 and a maximum number of adjacent

ones of 5 on the serial line. Some of the bit patterns which cannot occur during regular data transmission

are used for special purposes. A pattern of 6 or more 1-bits is considered as the bus-idle condition. The bus

is idle, when no communication is currently ongoing. A pattern of 15 0-bits is recognized as the so-called

frame synchr

onization. This is the sequence to begin a new frame. The pattern “10101” is the so-called

frequency synchronization pattern. It is used after the frame synchronization to determine the transmitter’s

gross data rate.

Downstream communication is defined as data inputs at SIO1 and outputs at SIO2. This is the data flow for

write commands. Upstream respectively is defined as data inputs at SIO2 and outputs at SIO1. This is the

data flow for the read response.

Figure 10 - Single ended downstream command frame