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From: mark@SSD.HARRIS.COM (Mark Smith)
Newsgroups: comp.sys.tahoe
Subject: Re: What is the BTCS instruction ?
Message-ID: <2182@travis.csd.harris.com>
Date: 29 Jan 91 18:11:41 GMT
References: <9101241939.AA19540@csd4.csd.uwm.edu>
Sender: news@travis.csd.harris.com
Reply-To: mark@flipper.CSD.HARRIS.COM (Mark Smith)
Organization: Harris Computer Systems, Fort Lauderdale, FL
Lines: 64

In article <9101241939.AA19540@csd4.csd.uwm.edu> jgd@CSD4.CSD.UWM.EDU (John G Dobnick) writes:
>We received some code to fix a problem on our tahoe machine -- code
>which uses the BTCS instruction.  While the assembler seems to know
>what this is, it is _not_ described in any of the manuals we have
>available.  This makes it slightly difficult to understand just what
>the code is doing.  (I believe we have the most current manuals our
>vendor supplies.  This does not mean they are _really_ current, however.)
>
>My Question of the Day is:
>
>	What is this BTCS instruction?
>
>Ideally, I seek a response that provides all the information that the
>architecture reference manual supplies for the other instructions --
>to wit, instruction format, operand specifications, description of
>operation, "pseudo code" description of the instruction, condition
>codes, etc.
>

Chapter 8 (Instruction Set) of the Harris Computer Systems Division
HCX-7 and HCX-9  Architecture Manual (Publication Number 0830022-100) 
decribes the BTCS instruction as follows:


			BTCS
		BRANCH TO CONTROL STORE

Purpose:		Custom design of new instructions
Format:			opcode operand
Condition Code
Settings:		N Z V C
Exceptions:		None
Related Opcodes: 	0xCE - Branch to WCS
Detailed Description:	Branch to one of sixteen WCS locations. This
			instruction allows the addition of customized
			instructions for specialized functions.
Processing Details:	Branch to one of sixteen unique WCS locations
			pointed to by the last four bits of htet operand.

			btcs()
			/*********************************************/
			/*BRANCH TO ONE OF SIXTEEN WCS LOCATIONS     */
			/*********************************************/
------------------------------------------------------------------------
That's it. Hope it helps.

>Thank you for whatever information you can supply,
>-- 
>John G Dobnick  (JGD2)
>Computing Services Division @ University of Wisconsin - Milwaukee
>INTERNET: jgd@csd4.csd.uwm.edu             ATTnet: (414) 229-5727
>UUCP: uunet!uwm!csd4.csd.uwm.edu!jgd
>
>"Knowing how things work is the basis for appreciation,
>and is thus a source of civilized delight."  -- William Safire

Mark Smith
Internet:  mark@flipper.csd.harris.com
UUCP:      ...!uunet!travis!flipper!mark


Mark Smith
Internet:  mark@flipper.csd.harris.com
UUCP:      ...!uunet!travis!flipper!mark