boone@oce.orst.edu (Jeff Boone) (07/05/89)
I have been struggling with the DSP for the past week or so, and thought
I should tap into the net knowledge before I pull out the rest of my hair.
Below is the assembly code that <should> return the 256 sine entries in
the internal Y memory ROM. I used the initialization posted by Eric Thayer
to configure the DSP (although I don't use external memory, I still need
to enable the ROM data). The rest of the code just marches through the
sine table and sends the entries to the host.
What actually comes out is the first 128 entries in the table, some
garbage, and then part of the table started over from the first. And
to top it all off, it takes about 4 or 5 seconds to send this to the
host. JEEZ I might as well use my calculator! What gives?
Would some kind soul please shine the light on me. :-)
------------------------------ DSP Assembly code -----------------------
reset equ $0000 ; Address of reset vector
start equ $40 ; Start of program mem
data equ $100 ; Start of ROM sine table in Y mem
org p:reset
jmp >init
dup $40-2
nop
endm
org p:start
init movec #6,omr ; Data rom enabled, mode 2
bset #0,x:m_pbc ; Host port
movep #>$0001F7,x:m_pcc ; Both serial ports (SC0 not available)
bset #3,x:m_pcddr ; pc3 is an output with value
bclr #3,x:m_pcd ; zero to enable the external ram
movep #>$004000,x:m_cra ; Set up for external clock on DSP port
movep #>$002300,x:m_crb ; Read L/~R on IF1
movep #>$000000,x:m_bcr ; No wait states on the external sram
movep #>$00B400,x:m_ipr ; Intr levels: SSI=2, SCI=1, HOST=0
move #data,R2 ; Point R2 to the ROM sine table
nop ; Allow R2 time to update
move y:(R2)+,A0 ; Load first sine table value
do #256,end_out ; Send 256 sine values to host
xmt_dat jclr #1,x:$FFE9,xmt_dat ; Wait for host
move A0,x:$FFEB ; Send sample to host
move y:(R2)+,A0 ; Update A0 with next sine value
end_out
end $40
------------------ Program to read the sine table ----------------
#include <dsp/dsp.h>
#include <stdio.h>
main()
{
int count;
int output[256];
DSPBootFile("sine.dsp"); // Load the dsp image file
DSPGetRXArray(output,256); // Get the 256 sine values from DSP
for (count=0; count<256; count++) // Print the values
printf("0x%X\n",output[count]);
}eht@f.word.cs.cmu.edu (Eric Thayer) (07/05/89)
DSPBootFile() opens the dsp in a mode such that if the MSB of the data in the
HTX is high, the DSP driver interprets this as an error code. Hence the
garbled data for half of the cycle.
I sent NeXT a bug report about this one and they sent me a work around. I'll
post their work around when when I get into work.
And as you've noticed, the I/O throughput of the standard calls is not so
good. There are better ways to do I/O (dsprecord uses them for instance), but
so far I have not been able to see any example code for it.
DSP coding on the NeXT requires perseverance. Also ping ask_next about these
things so corporate NeXT is made aware of the issues they have to address.
--
Eric H. Thayer Carnegie Mellon School of Computer Science
(412) 268-{8724,6973} 5000 Forbes Ave, Pittsburgh, PA 15213