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1. Introduction
2. Binary Block Read Mode and Structure
2.1. Compressed Binary Block Read Sequence
2.2. Compressed Binary Block Structure
2.2.1. Data Block Structure
2.2.2. Record String Structure
3. Compression Decompression Methods
3.1. Table Decompression
3.1.1. Nibble Positioning
3.1.2. Record String Format
3.1.2.1. Data Decompression Considerations
3.1.3. Table Decompression Example
3.2. Space Compression
4. DLE Stuffing
5. The Cyclic Redundancy Check Option
5.1. Calculation
6. Other Binary Read Commands
6.1. Continuous Binary Block Read
6.2. Send Binary Information Block
7. Customer Service
PollCat NetLink B

2.2. Compressed Binary Block Structure

 

As shown in Figure 1, the compressed binary block includes the following items:

 

 

Figure 1: Compressed Binary Block Structure

STX: The ASCII STX character (Control B, 02 hex)

Character Count: A 2 byte, binary count of the number of characters of compressed binary data (all characters in the data block). This count does not include the STX character, the count itself, the ETX character, the CRC character or any DLE stuffing characters.

Data Block: Contains a Block Header and a series of record strings as described in Section 2.2.1.

ETX: An ASCII ETX character (^C ([Ctrl] plus [C], 03 hex).

CRC Code: A 2 byte, binary CRC code. The CRC is calculated on all bytes transmitted except the DLE stuffing bytes, which are added at transfer time. The CRC calculation method and DLE stuffing function are described later in this document.