circular buffer logic

[nileshsurya 0]

hi there all PLC ppl i want to write a circular buffer logic in a CLX L-63 cpu. the basic concept is as follows there will be a buffer of 10 similar elements in the CLX processor these 10 buffers will serve the purpose of communicating data to different instances of HMI so when a request to read/write data comes from a HMI the data is loaded in the first element of the buffer and the buffer index is incremented by one. the increment is made to make the buffer ready if another instance of HMI demands the same or similar data.when this is done the buffer index is again incremented by one and this continues in a circular fashion i hope you all understand my point i will throw more light on this in tomorrows post but right now it wud b of gr8 help if anybody tells me how to approach to do this logic it is very important and urgent for me to get this logic done in a very short span of time, so i need help from all u PLC experts very urgently waiting for reply,which will be of gr8 help 2 me thanx in advance Regards Nilesh Surya AB PLC Programmer

[Ken Moore 23]

Can't help you out. But I must ask why? Doesn't appear to be very effecient, why not just read the data from the HMI without the buffer?

[nileshsurya 0]

i require the buffer because the buffer is required to give the data of some 150+ relays to the HMI through a common tag(which is naturally this buffer) as and when required dynamically. i hope u r getting my point sir so if HMI # 1 requests data of smart relay # 1 then it is supplied in bufer number 1 and the index is incremented. now if HMI # 2 requests data of SMART RELAY # 2 then it is given in buffer # 2 and so on hope ur gettin it sir regards Nilesh Surya

[dleehanson 0]

not totally following. How do you assure that the polling order is correct? What relay are you talking about? What HMI are you using, is it server based? What comms. Ethernet?

[Ghettofreeryder 0]

i have a program which uses the modbus protocol i can send you if you wanna see how i rotate my poll, which is the same thing u need to do. The original program wasnt written by me(brutally slow scan time) but itll show you how to do the poll rotation. Its in ladder program #29 FORT_ENERGY_13_03_W5M_DEC_1_AS_LEFT.RSS Edited 2 Dec 2005 by Ghettofreeryder

[Jeevan 0]

Hi Nilesh, Jeevan From Philippines email-jeevan.puthran@rediffmail.com. Saw your Query but unable to open the prog. since no Rslogix-500 installed here. However read my posted Query on 1784-PCIC(S) and if possible reply. will be in touch via. mails.