ENMET EX-6100 Series - Manual (Page 24)

EX-6100 ENMET Corporation
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A.3 Communications Protocol
The communications protocol used by the EX-6100 is used for communications between devices connected via an RS232
connection at 19200 baud, 8 data bits 1 stop bit, no parity. This point-to-point, P2P, protocol is a frame-based protocol.
A.3.1 Hardware connections
PC 9-way ‘D’ connector EX-6100 connection
2 Tx
3 Rx
5 0V
PC 25-way ‘D’ connector EX-6100 connection
3 Tx
2 Rx
7 0V
A.3.2 Control Byte Constants
The following control byte constants are used in the P2P protocol.
Read, RD = 0x13 (00010011)
Data Link Escape, DLE = 0x10 (00010000)
Write, WR = 0x15 (00010101)
Acknowledge, ACK = 0x16 (00010110)
Negative Acknowledge, NAK = 0x19 (00011001)
Single Data Frame, DAT = 0x1A (00011010)
End of Frame, EOF = 0x1F (00011111)
Write Password 1, WP1 = 0xE5 (11100101)
Write Password 2, WP2 = 0xA2 (10100010)
A.4 Frame Structure
The start of a frame is indicated by a DLE byte followed by the type of frame to follow (RD, WR, ACK, NAK, DAT). The end
of frame is indicated by a DLE byte followed by an EOF byte.
Note: Each of the constants has bit 4 set and so is slip-resistant (i.e. if shifted this bit will be out of position). The values
have a Hamming Distance of 2 (each code is at least 2 bits different from every other code).
Any DLE bytes that occur between a frame’s start and end are prefixed with another DLE (byte-stuffing).
Following the EOF is a 16-bit checksum of the entire frame, each byte is added to produce the checksum.
A.4.1 Variables
Each piece of accessible data on a device is referred to as a Variable. Each variable is referenced by a Variable ID. A variable
ID may be any number of bytes long.
The available Variables and their corresponding Variable IDs depend on the type of device, but here are a few examples for the
EX-6100 :
General Configuration 0x00
Live Data 0x01
Zero Sensor 0x02
Span Sensor 0x03
Version Information 0x04
Firmware Update 0x05
The structure of the data returned in each variable usually depends both on the type of device and the version of firmware
running on the device.
Refer to device documentation for more information.