| Title: | -={ H A C K E R S }=- |
| Notice: | Write locked - see NOTED::HACKERS |
| Moderator: | DIEHRD::MORRIS |
| Created: | Thu Feb 20 1986 |
| Last Modified: | Mon Aug 03 1992 |
| Last Successful Update: | Fri Jun 06 1997 |
| Number of topics: | 680 |
| Total number of notes: | 5456 |
How accurate are VMS Timer Services? Specifically, I have to write an application that sends 3-4 line messages out of up to 20 async terminal ports. Each port will have a separate "script" of the messages to be sent and the delay between each message. I'd like to use the Timer Services to handle the delay between messages, but I'm concerned about the delay accuracy when we're driving 20 ports. BTW, this is on a uVAX-II, with most of the ports being 300 or 1200 baud. The desired timer accuracy is 0.1 seconds. Also, would it be better to single-thread all of the output processing through one process or multi-thread output with 1 process/port or some other scheme? Regards! John
| T.R | Title | User | Personal Name | Date | Lines |
|---|---|---|---|---|---|
| 200.1 | SANFAN::HAYESJO | Wed Jan 29 1986 20:56 | 3 | ||
BTW, I see I got Note 200! Do I get a prize? John | |||||
| 200.2 | MAASSG::RMURPHY | Wed Jan 29 1986 23:59 | 15 | ||
Hi John! Well, with some care, using timer services should provide you the accuracy that you need. By care I mean that you should make sure that when a timer fires, the process doing the output is not pre-empted by some other process. As far as the design is concerned, I would probably use a single process, with AST's scheduled to do the output. You'll just have to make sure that this process has enough buffered I/O count, bytlm, and astlm to do all the outputs as necessary. Do the output operations with $QIO (not QIOW) to minimize the AST latency. With a little thought, it shouldn't be that hard to meet a 0.1 second accuracy goal. It seems to me that decoding the "Scripts" would be more work than doing the outputs themselves... -Rick | |||||