MagTek MCP - Manual (Page 9)

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SECTION 2. TRANSPORT FRAME FORMAT
COMMON FRAME FORMAT DEFINITION
Below is the diagram of the common frame format:
DA SA PCB LEN HEDC DATA EDC
The frame consists of a frame header, a variable-size opaque data field and an error detection
code (EDC).
FRAME HEADER
The frame header comprises the following fields:
• DA – destination address
• SA – source address
• PCB – protocol control byte
• LEN – length of the data (in bytes)
• HEDC – error detection code of the frame header
The following sections describe each field and how it is used. Below is the diagram of the frame
header:
DA SA PCB LEN HEDC
Node Addresses
The destination address (DA) defines the node to which the frame is sent. The source address
(SA) identifies the node that sent the frame.
The node address values are encoded as follows:
Address (Hex) Definition
00 Host node address (the PC)
01 Device node address
02-FF RFU (Reserved for Future Use)