Date: Tue, 23 Jan 1996 18:29:06 GMT From: k.iacovou@ic.ac.uk To: www@freebsd.org Subject: i8237A port problem? Message-ID: <5406.199601231829@ohm.ee.ic.ac.uk> Resent-Message-ID: <Pine.BSF.3.91.960123200421.7310G@fieber-john.campusview.indiana.edu>
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Hi - I am currently involved in a College project which involves low-level programming of PC sound cards. I read part of the FreeBSD Handbook as regards DMA, and I would like clarification on a couple of points, if possible. The DMA command registers quoted in section 18.3.5 of the Handbook for the first DMA controller are from 0x10 through 0x1e for Command/ Status register through to Write All Mask Register Bits. However, this is at variance with information given on page 212 of "The Handbook of Hardware and Software Interfacing for the IBM-PC", which gives the port numbers as 0x08 through to 0x0f for the same ports. This is supported by a brief article included in the so-called Soundblaster Freedom Project by Josh Cohen, which states, and I quote: "Disable the channel you wish to set up. If we use channel 1 we send 0x05 [=0000 0101b] to address 0x0a" (Port 10 is given as the Write a Single Mask Register Bit, so writing 0x05 to it would set the bit pertaining to channel 1). Also: "Clear the Byte Pointer...write any value to 0x0c" (0x0c is given as the Clear Byte-Pointer Flip-Flop for DMA Controller 1). The same information is also partially given in an article titled "Programming the Soundblaster 16 DSP" by Ethan Brodsky which gives 0x0a, 0x0b and 0x0c as the Write Single Mask Register, Write Mode Register and Clear Byte Pointer Flip-Flop respectively. Oddly enough, IBM's own Technical Reference for the PC-AT (Vol 1) does not give the port map for the first DMA controller, but only for the second. Might it be possible to have this message passed on to the person who compiled the DMA section in the Handbook so that either it be corrected or that I might have my query answered? Many thanks in advance, K.Iacovou (kgi@ee.ic.ac.uk)
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