Path: utzoo!utgpu!jarvis.csri.toronto.edu!rutgers!rochester!pt.cs.cmu.edu!f.word.cs.cmu.edu!eht
From: eht@f.word.cs.cmu.edu (Eric Thayer)
Newsgroups: comp.sys.next
Subject: Re: DSP help needed
Keywords: off chip memory
Message-ID: <5264@pt.cs.cmu.edu>
Date: 20 Jun 89 23:58:18 GMT
References: <5262@pt.cs.cmu.edu>
Distribution: usa
Organization: Carnegie-Mellon University, CS/RI
Lines: 18

This code fragment configures the DSP environment 'properly.'  I believe that
you are right in saying that external ram seems to be disabled.  This fixed
my problems with using external ram.  The reset vector should be:
	jmp	>init

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
_reset
-- 
Eric H. Thayer		Carnegie Mellon School of Computer Science
(412) 268-{8724,6973}	5000 Forbes Ave, Pittsburgh, PA 15213
--