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*BL (Buffer Limit Command) - Printable Version

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*BL (Buffer Limit Command) - Beery Miller - 02-20-2018

I've been trying to understand what I may be able to do with the *BL command with a Geneve 9640 computer.

Tim Tesch has a program called PORT that works well all the way up to 38400 on file transfers so I know it can be done.  Myself, i am working on a different terminal emulator and I am getting a strange and reproducible response when doing Xmodem (128 byte) downloads.

I have not figured out what, but I can start a download at 38400 baud and the moment the 128 block reaches a transfer of 10,112 bytes, I error out.

I have experimented with the video display as it updates the bytes transferred, so I know the routine when it goes from a 4 character display to a 5 character display of bytes transferred, is one issue.  I am right on the cusp of the CPU speed with too many cpu cycles away from capturing RS232 data.  When I comment out the display of bytes transferred, it continues on past 10,112 until some other point when it then errors out.

At first, I thought it may have been tied to interrupts or the handshaking, but there may be something happening I am not fully comprehending.  When I change the buffer limit with a AT*BL64, I do not even get the first block.  If I go to the higher end of the limit, I get some other responses.

So, what I am wondering is what is the WiModem232 doing with a smaller buffer versus a larger buffer between a BBS (Mystic BBS software) back to the modem from where it then connects to my software and computer.  I hope that is explained well enough.

Could there be a preferred or optimum BL setting for packet size with the file transfers.  

Please note, it has been years since I have done any significant programming, and I am still pretty green at coding for an RS232 interface.  However I saw some subtle differences if I varied the BL setting when I thought any changes to that setting should have had no impact on the file transfer.

Any insight would be appreciated.

Beery


RE: *BL (Buffer Limit Command) - admin - 02-20-2018

The BL just sets the maximum number of bytes that are allowed to arrive at the WiModem232 before it changes CTS to stop the computer from sending any more data to it.  I have never actually seen a need for this, and this was just left over from testing.  The BL option can probably be removed and left hard coded at default.

Do you have a RTS/CTS cable?  Are you using AT&K1 to enable the hand shaking?


RE: *BL (Buffer Limit Command) - Beery Miller - 02-20-2018

(02-20-2018, 09:02 AM)admin Wrote: The BL just sets the maximum number of bytes that are allowed to arrive at the WiModem232 before it changes CTS to stop the computer from sending any more data to it.  I have never actually seen a need for this, and this was just left over from testing.  The BL option can probably be removed and left hard coded at default.

Do you have a RTS/CTS cable?  Are you using AT&K1 to enable the hand shaking?

I am using AT&K1 and with Tim's Port program and the same cable configuration, it works fine.

As far as whether it is a RTS/CTS cable, I am going to have to go and dig further into how it was wired up.  I'm just not sure.

Beery