Copyright 2005 –
2
7 T
x
DRAWING NO
2506799
REV
C
SHEET 3
1. SCOPE
This document specifies the serial interface requirements for the lamp ballast. This document
defines: electrical interface definitions, connector pin assignments, communication protocol,
communication parameters, instruction set definition and communication timing.
2. Reference Documents
• EIA-RS-232-C Interface Specification
3. Communication interface
The implemented UART interface is a two (2) wire asynchronous interface with no handshaking.
It consists of a transmit data signal (TxD) from the lamp ballast to the controller board and a
receive data signal (RxD) from the controller board to the lamp ballast. The timing is similar to
the RS-232C standard with the exception of the voltage levels.
4. Communication Protocol
The user, controller board, shall send an instruction via the receive data signal (RxD). The lamp
ballast shall determine if the instruction is a command or query. For a command, address 70h –
7Fh, the ballast shall reply back to the controller board with an echo via the transmit data signal
(TxD). For a query, address F0h – FFh, the ballast shall reply back to the controller board with
an echo and response via the transmit data signal (TxD). Figure 1 shows a flow diagram of the
communication protocol.
Lamp Ballast
Waitng for
Instruction
User
Command or
Query?
Receive
Instruction
Echo +
Response
Echo
QueryCommand
Execute
Command
Wait for
SCI/SYNC
Figure 1 Communication Protocol Flow