CBMSTUFF FORUM
Buffering capability - Printable Version

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+---- Thread: Buffering capability (/showthread.php?tid=445)



Buffering capability - Beery Miller - 01-12-2018

I've got more of a technical question on the hardware

I am doing some programming and testing of a terminal emulator with the WiModem232.  I've noticed with the code I am using, I am getting some dropped characters and they are pretty reproducible in location.  Other software written by someone else is not experiencing the issue.

So, my first question is, how much of a buffer (bytes/characters) does the WiModem232 have?

And secondly, I am trying to determine which scenario below is the issue:

A) If characters have not been pulled from the buffer before it has exceeded capacity, do the additional characters get dropped?

or

B) Does the oldest characters in the buffer get overwritten and the WiModem232's current character pointer get updated to reflect the oldest character in the buffer?

Any feedback would be appreciated is appreciated as I try to dial in my polling requirements of the modem so I do not lose characters.

Beery


RE: Buffering capability - admin - 01-12-2018

The buffer is over 2K for the RF portion.  Are you using RTS/CTS flow control?  With that enabled, you can't have an issue.  Without flow control, you can easily get dropped characters at around 9600 baud.  I run this at 115200 baud on the Amiga, but the hardware is suppose to be able to handle up to 1 megabaud.  I have PC serial card coming to test that.


RE: Buffering capability - Beery Miller - 01-12-2018

(01-12-2018, 12:35 PM)admin Wrote: The buffer is over 2K for the RF portion.  Are you using RTS/CTS flow control?  With that enabled, you can't have an issue.  Without flow control, you can easily get dropped characters at around 9600 baud.  I run this at 115200 baud on the Amiga, but the hardware is suppose to be able to handle up to 1 megabaud.  I have PC serial card coming to test that.

I was running at the default baud rate.  Will need to do some more testing.

Beery


RE: Buffering capability - admin - 01-12-2018

The default baud rate is 300 baud. You can "out type" that. Smile


RE: Buffering capability - Beery Miller - 01-13-2018

(01-12-2018, 07:11 PM)admin Wrote: The default baud rate is 300 baud.  You can "out type" that.  Smile

I forget which it was.  With the flow control and cabling of the software I am using for the Geneve 9640, I was losing characters.  If I turn on just normal interrupts, I could run at least 19200 depending upon the terminal emulator I was using.  I forgot what the baud rate was I was testing yesterday, but you are right, it was not 300 baud.

Beery


RE: Buffering capability - admin - 01-13-2018

I guess it depends on the speed of the computer. Something like an Amiga 1200 doesn't need flow control even at 57600 baud. However, some retro machines need flow control at anything over 1200 baud.

Remember that RTS/CTS flow control is the default jumpered setting (along with DTR/DSR tied together). If you need DTR or DSR for flow control, then you would need to cut the 3 traces and jumper as necessary for your system. Most of the time, this is only needed for old printers. DTR/DSR was sometimes used to hang up the connection.