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SI8 Owen - pulse counter

Guide to counter SI8 Owen   Dowmload   Sive: 1.3 Mb

§1 Description of the pulse counter Owen SI8

Pulse counter - is one of the oldest and simplest devices, industrial electronics.
Requirements for them are well known and implemented. The company is not able to make a good pulse counter is unlikely to be able to do something worthwhile.
Manufacturer Oven produces one of the most popular microprocessor counters, although there are a lot of significant shortcomings. I will describe the experience of this counter, its features (flaws). Full functional description SI8 you can find on the website of Aries , I set myself the goal to give a full description SI8.
If you look at the functionality, everything looks good. But to understand how it works let us compare SI8 with other counters. For comparison, take the meter AS-8 Kracht and DA-5 Pepperl + Fuchs. By functionally SI8 exceed these counters. The question is on the little things: how it works?

Fig. 1 Impulse counter DA-5 Pepperl + Fuchs
DA-5 Pepperl+Fuchs

Fig.2 Pulse counter AS-8 Kracht
AS-8 Kracht

Fig.3 Pulse counter SI8 Owen
SI8 Owen

§ Little things mean nothing - they define it!

§3 The protocol SI8 Owen via RS-485

Of the above it is clear that the greatest interest is the use of this counter in the network RS-485, if it was not possible, I would call this computer useless (because of step 4 § 2).

The protocol with the devices Owen   Dowmload    Size: 1285 kb Changed:30.06.2009

Secondary device counters (slave) connected to a serial cable twisted pair "with the wave impedance of 100 ohms. The cable is acceptable up to 1000 meters. At last the secondary device, you must install the terminator. Terminator is the usual resistance, its magnitude must be equal to the characteristic impedance of the cable (in this case 100 ohms). It is required for suppression of the secondary wave, which is reflected from the end of the line of communication, as well as for current feeding "twisted pair".

Fig.6 Construction of the line RS-485 communication from the leadership of the AC3 Aries
Liniya connection RS-485 Oven

Note that the twisted pair should approach and depart from the secondary contacts of devices, and not as it is drawn in the leadership of Aries, where the devices are connected the wires tapped from the secondary devices to a communication line (it's not technically literate).

In RS-485 protocol Aries provides the presence of only one lead (master), usually a PC with a program survey of secondary devices. Counters SI8 serve as slaves (slaves), they can not themselves initiate the exchange of data and waiting for the command to request data from the lead. Upon receiving the command data request from a leading computer sends the requested data to the network RS-485. This computer does not check the free or busy line of communication and after about 1.1ms gives the answer. This is a shortcoming of the protocol OWEN, because it may cause conflicts in the communication line. In addition, if you use converter interface in which the transmit / receive data in a communication line is selected signal RTS (AC3 Aries), then there is always a chance not to have time to remove its activity within 1 ms, which leads to loss of integrity of the response from the counter. This is particularly sensitive to the OS XP / Vista where the suspension of your program can significantly exceed the interval of 1ms. Settings latency response in the counter SI8 not. To solve this problem, use the converters interface with automatic transmit / receive (AS3M Aries). I solved this problem with the AC3 closure signal TD to RTS jumper and does not use the RTS signal from the COM port of a PC. With such a connection AC3 begins to work as AS3M. Interestingly, the company has developed ARIES AS3M the same way or not?

Another feature of the protocol Aries (and probably its lack) is the transfer of bytes of information tetrad-character way. That is, each transferred byte is divided into two tetrads, each of which is assigned a predetermined symbol, these symbols are transmitted in a communication line. On the receiving side for receiving bytes of information necessary to properly glue these notebooks.

Table 1. Accepted OWEN characters to display tetrads
tetrad symbol bytes of which pedalaetsya on line (character code)
0000 G 47hex
0001 H 48hex
0010 I 49hex
0011 J 4Ahex
0100 K 4Bhex
0101 L 4Chex
0110 M 4Dhex
0111 N 4Ehex
1000 O 4Fhex
1001 P 50hex
1010 Q 51hex
1011 R 52hex
1100 S 53hex
1101 T 54hex
1110 U 55hex
1111 V 56hex
The disadvantage (or more precisely unused capacity), I think here is that if 100% redundancy package, Aries does not use the possibility of correcting bit errors, but only offers to detect them. At the same address space character located together, without gaps, thereby significantly reducing the detection of bit errors (as byte characters are too similar, and the probability of single-bit errors is the highest!). Modern computers should use corrective excessive coding

In addition to the character set for the transfer of tetrads are two marker parcels (frame).
This is a # (code 23hex) which serves to indicate the beginning of a parcel (frame) and the symbol CR (code 0Dhex) end of the parcel.

Fig.7 Structure of the frame protocol OWEN
The structure of the frame protocol OWEN

Bim frame - announces the start of a parcel
Address of the device in the network - can be 8 or 11 bits
Beat Request -equals 1 if the command request parameter meter, 0 - if this response counter
Data block length - indicates block size in bytes
Id team- hash convolution parameter name
Data block- are transferred to the meter readings
Check sum - checksum of the package without markers
Marker end of the frame - informs about the end of the parcel
Таблица 2. Counter SI8 has three parameters:
parameter name hash-fold tetrad symbol description command
DCNT C173hex SHNJ meter readings
DSPD 8FC2hex OVSI reading flowmeter
DTMR E69Chex UMPS readouts timer

This shows that you can only read my meter, program the settings on the network can not.
For example to read the meter readings with Adr = 4, should be sent to the network the following premise:
# GKHGSHNJNPHU (CR) in hex format, 23 April 1910 C1 73 79 1E 0D
In response, we get (if you count the zeros) answer:
# GKGKSHNJGGGGGGGGBCD5 (CR) in hex format, April 23, 2004 C1 73 00 00 00 00 BC D5

To create a query and reading the parcels necessary to calculate the checksum. As I said to compute the checksum takes the whole premise except markers and checksum (naturally) and made it a byte convolution with a polynomial 8F57 hex by the algorithm shown in Figure 8.

Fig.8 algorithm for computing the checksum protocol OWEN one byte
Algoritm calculating CRC protocol OVEN

The question remains for hash-fold parameter name, describe in detail I did not will. OWEN designers here for some reason namudrili. The names of the parameters of the device are written clearly displayed in the ASCII transmission tetra-characters in the ASCII. Why convert ASCII to ASCII. For example the parameter names DCNT-> SHNJ, DSPD-> OVST, DTMR-> UMPS always displayed in the same. Aries offers to the parameter name in ASCII (eg DCNT), put it in dvoychny species is not on the code page to ASCII, and the code page invented OWEN. Then make a hash-convolution of a polynomial 8F57hex the algorithm somewhat different from that presented in Figure 8 and the resulting hash-convolution of the transfer in a notebook-symbols on the table Aries. What caused such a thought process of developers I can not explain, why did not immediately call options as needed to insert into the frame?

You may not use all of these changes to work with SI8, you only need to know what the parcel needs to be sent to each address unit. It's easier to do manually on a sheet of paper than to write algorithms for all these treatments.
You can use the table 3, where the parcels are counted for the first 15 addresses.

Таблица 3. Make a request for SI8 without markers
instrument address format запрос DCNT request DSPD request DTMR
01 hex 0110C173A818 01108FC2D5F5 0110E69C92C6
02 hex 0210C173E71A 02108FC29AF7 0210E69CDDC4
03 hex 0310C173DDE4 03108FC2A009 0310E69CE73A
04 hex 0410C173791E 04108FC204F3 0410E69C43C0
05 hex 0510C17343E0 05108FC23E0D 0510E69C793E
06 hex 0610C1730CE2 06108FC2710F 0610E69C363C
07 hex 0710C173361C 07108FC24BF1 0710E69C0CC2
08 hex 0810C173CA41 08108FC2B7AC 0810E69CF09F
09 hex 0910C173F0BF 09108FC28D52 0910E69CCA61
10 hex 0A10C173BFBD 0A108FC2C250 0A10E69C8563
11 hex 0B10C1738543 0B108FC2F8AE 0B10E69CBF9D
12 hex 0C10C17321B9 0C108FC25C54 0C10E69C1B67
13 hex 0D10C1731B47 0D108FC266AA 0D10E69C2199
14 hex 0E10C1735445 0E108FC229A8 0E10E69C6E9B
15 hex 0F10C1736EBB 0F108FC21356 0F10E69C5465

After receiving a response from the counter in the data field will be his testimony in a symbolic form. Turn characters into binary tetrads per table 1. The resulting binary number to be transferred to the meter readings according to the data format defined by Owen.

It is a sign (S), decimal order (Exponent) indicates position of the decimal point
(0 for integer, 1 for the number of tenths, etc.) and non-normalized mantissa (Mantissa).
S - significant bit
Exponent - the following 3 bits
Mantissa - the remaining bits (the length of the mantissa is determined by the size of the data fields)
The total length must be an integer number of bytes
numbers can be calculated as
The mantissa can be expressed as a binary and in binary-coded decimal form.
For example:
-10.38 Expressed as 0xA01038 in binary-decimal mantissa
or as 0xA40E, that is, the bytes shorter when its binary representation.

For DSPD like DCNT only without the sign bit

0-th byte - hundredths of a second;
1-st byte - seconds;
2-nd byte - minutes;
3, 4, 5-th bytes - watch.

§4 Conclusion

As I wrote in the beginning of the article SI8 one of the best domestic counters, and this is not a sneer.
SI8 was released in the 90 years and in that time was quite advanced. He has more than 10 years in operation. Manufacturer Aries is somewhat delayed the modernization of the counter, and this story I wrote in the hope that they will heed the desire of consumers in the development of a new counter. As far as I know to produce ready counter SI30 ARIES (I hope he will not have 30 digits on the screen:))
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