sfm3166@ultb.UUCP (S.F. Modi) (08/01/89)
Subject: IBM interupt handler for PS2
Newsgroups: comp.sys.ibm.pc
Netters
I am trying to write an interupt driven I/O handler on the IBM
PS 2. I am replacing the interupt vector OB and OC with hooks to my
routine for interupts. The address I am using are 3F8 and 2F8 for com1
and com2 resp. The interupt routine serial driver works fine with and
without loopback for IBM PC XT but fails with PS/2 or AT. Am I doing
something wrong in the vectors ? Any one have a simillar problem ?
Any help will be greatly appreciated. Please mail replies to
{rutgers,cornell}!rochester!rit!ultb!sfm3166.
thanks
Sohrab Modi
mail address : {rutgers,cornell}!rochester!rit!ultb!sfm3166kevin@msa3b.UUCP (Kevin P. Kleinfelter) (08/03/89)
sfm3166@ultb.UUCP (S.F. Modi) writes: >Subject: IBM interupt handler for PS2 >Newsgroups: comp.sys.ibm.pc > I am trying to write an interupt driven I/O handler on the IBM >PS 2. I am replacing the interupt vector OB and OC with hooks to my >routine for interupts. The address I am using are 3F8 and 2F8 for com1 >and com2 resp. The interupt routine serial driver works fine with and >without loopback for IBM PC XT but fails with PS/2 or AT. Am I doing >something wrong in the vectors ? Any one have a simillar problem ? I have found no problem in this area. The following logic works, for me on PC,XT,AT,PS/2: out (0x21,MASK_FOR_MY_COM_PORT_INTS) ; shut of ints from com? wait-2-microseconds-or-more in (comport_data_reg) ; in case there is already data save_old vector (3F8 or 2F8) out (0x21, MASK_MY_COM_INTS_ON) ; enable ints from com? Perhaps you are leaving out one of the steps, and accepting default values left there by boot (and perhaps they are different on the different machine). The following ports are of interest (for COM1) 3F8 TD/RD 3F8 BaudRate (low) 3F9 BaudRate (high) 3F9 Enable interrupts 3FA Interrupt ID 3FB Select amongst uses of 3F8,3F9 3FC ModemControl (output) 3FD LineStatus (input) 3FE ModemStatus (input) 021 Interrupt Controller Note: Accesses to the 8250 must be at least 2 microsec apart or it will SEIZE-UP (a technical term meaning "bust"). A useful text is "IBM Personal Computer from the Inside Out". (Yes, I know you really know how to do all this. I'm just suggesting that you do an operation by operation compare with something that works on all machines, to see what you've missed.) -- Kevin Kleinfelter @ Management Science America, Inc (404) 239-2347 gatech!nanovx!msa3b!kevin