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Read Command Example
Read a value from registers 13,14 on slave#52
by sending –
[hex]
station address
34
03
00 0C start-reg hi,lo (NB h14=20 addresses register 21)
00 02 quantity = 2 registers
01 AD checksum = hi,lo
A Correct Response, With A Value -55.2317 (Hex C25CED51) Would Then Be
[hex]
station response
34
03
04
ED 51 C2 5C
AA D4 checksum = hi,lo
Execute Command Example
Execute command 101 on slave#17
by sending –
[hex]
station address
11
10
00 64 start-addr h64=100 → register 101
00 02 quantity = 2 registers
04
00 00 00 00 data (value irrelevant)
A0 B4 checksum = hi,lo
The Acknowledge Response Is Then
[hex]
station response
11
10
00 64
00 02
02 87 checksum = hi,lo
The Mantrabus-II Protocol
Mantrabus-II is a two-wire system where data is transmitted & received over a common pair of wires. For this reason
the framing character must not be sent in a reply from the responding DCell.
The protocol ensures this does not occur by splitting byte data into nibbles with the exception of the framing
character & station number.
Framing Character
The framing character for Mantrabus-II is FEh, (this being different from the older Mantrabus-I FFh to allow the two
protocols to be mixed on one bus).
Checksum
Both Host & Device send their EXOR checksum of all data sent, excluding framing character, in nibble format the MS
nibble being first.
eg. EXOR Checksum of data is A7h. Checksum characters sent = 0Ah, 07h
Data Transfer
Data is both sent and received as 4 bytes split into 8 nibbles following the station number, plus two nibbles of
checksum.
Floating-Point Data Format
All data sent & received in Mantrabus-II is in the IEEE floating-point format, this being a 4-byte floating-point
number. The byte containing the sign & exponent is sent first, with the LS byte of the mantissa being last.
The Memory Layout Of The 4-Byte Floating-Point Numbers Is:
MSB
31
30-23
LSB
22-0
Micron Meters DCell & DSC User Manual
function code
function
byte-count
data
function code
byte-count
info copied from command ...
Sign bit ,
1=negate
Exponent,
7-bit excess-127
Mantissa,
23-bit fraction with implicit 1
52
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