Transmit Buffers save the day

For the past several days I have battled with a Mazatrol M Plus controller connected to a Mazak V65 machine center and after rigging up a 25 to 9 pin null cable was having no luck sending programs from the PC to the Mazatrol.  We were able to send from Mazatrolt to PC. Hmm.. tried everything under the sun.

Different cable – same diagnosis. Different PC – same diagnosis.  Then returning after my lunch break I pondered FIFO buffers.  Geeky yes. Irrational – no.

Turns out the Transmit Buffer on the PCI Serial ports default to an ITL or transmit buffer of 14 – whereas the incoming buffer size on the 10+ year old Mazatrol is likely less. I  changed it to 4 and low and behold we were sending and receiving.  The Receive Buffer on the PC would work at default 16 due to the lower incoming buffer size of the Mazatrol.  When you think of it like a geek – IT does make sense.