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LevelPRO -
Multiple Tank Level Processor
EX-1803
King Bus ASCII Communications
Communications Technical Specifications:
• Two wire half-duplex with isolated ground
• Automatic signal level shifting for point-to-point
(RS-422) and multi-drop (RS-485).
• ASCII character transmission formatted as (0) start
bit, (8) data bits and (1) stop bit.
• Standard baud rate up to 19.2 kbps.
Host Polling Protocol
The host device must query LevelPRO processors to
receive level data and/or to change specific gravity
values. The query should be configured using the
following ASCII code formats.
Request Level Data:
#NNN*
#
= Beginning character, first character sent ($23 Hex)
NNN
= 3 character ASCII polling address, 001-256
*
= Terminating character, last character sent ($2A
Hex)
Change Specific Gravity:
#NNN_S.SSS*
#
= Beginning character, first character sent ($23 Hex)
NNN
= 3 character ASCII polling address, 001-256
_
= Space character ($20 Hex)
S.SSS
= 5 character specific gravity includes decimal
($2E Hex) character
*
= Terminating character, last character sent ($2A
Hex)
LevelPRO Response Format
Communications output from individual processor in
response to query by host.
31 Character Response:
NNN_S.SSS_XLLLLLLLL_UUUU_CCCC<CR><LF>
NNN
= 3 character ASCII polling address, 001-256
_
= Space character ($20 Hex)
S.SSS
= 5 character specific gravity includes decimal
($2E Hex) character
_
= Space character ($20 Hex)
X
= Status code; B (blank), F (full), R (reserve/empty),
C (calibration mode)
LLLLLLLL
= 8 character level value, leading zeros
required if applicable
_
= Space character ($20 Hex)
UUUU
= 4 character units abbreviation/code in the
form, GALS
_
= Space character ($20 Hex)
CCCC
= Check sum in ASCII representation of a
2-byte number in the form, 0FE5
<CR>
= Carriage return ($0D Hex)
<LF>
= Line feed ($0A Hex)
Sample Response:
001_1.032_B00023900_GALS_04DC<CR><LF>
Checksum does not include the last space character
($20), carriage return ($0D), line feed ($0A) or the
checksum value itself.
The actual hex data transmission:
$30 $30 $31 $20 $31 $2E $30 $33 $32 $20 $42 $30
$30 $30 $32 $33 $39 $30 $30 $20 $47 $41 $4C $53
$20 $30 $35 $34 $33 $0D $0A
(Underlined values are not added to the preceding bytes
to create the checksum.)
The King Bus ASCII protocol is used by LevelPRO
processors having the KINGCODE.HEX
microcontroller code. These units are designated by
serial numbers beginning with the letter D.
For LevelPRO processors that employ MODBUS
compatible communications, refer to EX-1803-2
protocol manual. Units designated by serial num-
bers beginning with the letter M have the
KINGMBUS microcontroller code.
