/ THIS IS A DISASSEMBLY OF THE RX28 BOOT 
/ LOADER IN TABLE 1-8 OF the EK-RX012-PS-002 
/ "RX01 & RX02 POCKET SERVICE GUIDE".
/ I got it from David Gesswein:
/ http://www.pdp8online.com/ftp/software/rx02boot/

	LCD=6751
	SDN=6755
	SER=6754
	STR=6753
	XDR=6752

	*20
/  DEVICE IOT SYMBOLIC EQUATES
/
LCD=6751		/LOAD COMMAND
XDR=6752		/TRANSFER DATA
STR=6753		/SKIP IF READY TO TRANSFER
SER=6754		/SKIP ON ERROR
SDN=6755		/SKIP ON DONE
/
/
/
/
READ,	TAD	UNIT	/TRY NEXT COMBINATION OF DENSITY AND UNIT
	TAD	CON360	/ADDING IN 360
	AND	CON420	/KEEPING ONLY 420 BITS
	DCA	UNIT	/CYCLES 400,420,0,20,400,,,,,,,,
	CLL CLA CML IAC RTL /COMMAND TO READ DISK - MUST BE ON OMNIBUS!
	TAD	UNIT	/UNIT AND DENSITY
	LCD		/COMMAND TO CONTROLLER
	CLL CLA IAC	/TO SET SECTOR AND TRACK TO 1
	JMS	LOAD	/SECTOR TO CONTROLLER, LEAVES AC ALONE
	JMS	LOAD	/AND TRACK
LITRAL,	7004		/LEAVING A 2 IN AC; SERVES AS LITERAL
/
/  FOLLOWING IS PART OF WAIT LOOP, SAME SECONDARY BOOTS, OLD PRIMARY BOOT
/
RXSTRT,
XSTRT,	SDN		/HAS DONE COME UP; CODE STARTS HERE!
	JMP	LOAD+1	/NO, GO CHECK FOR READY TO TRANSFER
/
/  NOW, DONE OR ERROR
/
	SER		/SKIP ON AN ERROR, TRY ANOTHER DENSITY ETC.
	SNA		/NASTY, AC=2 FOR ABOUT TO DO SILO, 0 ON START-UP
	JMP	READ	/START-UP, GO SET UP UNIT, THEN READ TO SILO
	TAD	UNIT	/AC ALREADY 2, PUT IN UNIT, DENSITY
	LCD		/TO EMPTY THE SILO
	TAD	UNIT	/SET UP LOC 60 FOR OLD SECONDARY BOOT
	AND	CON360	/KEEPING UNLY DENSITY BIT
	TAD	LITRAL	/ADDING IN 7004, BECAUSE THAT'S WHAT SYS WANTS
	DCA	RX1SAV	/OLD SECONDARY BOOT MOVES IT TO HANDLER
CON360,	360		/LITERAL; EXECUTES IN LINE AS A NO-OP
/			/FALLS THRU TO NEXT PAGE OF LISTING
/
/
/  FOLLOWING CODE SAME AS OLD PRIMARY BOOT
/
	JMS	LOAD	/GRAB NEXT ITEM FROM SILO
	DCA	2	/TRADITION; SECONDARY BOOT STARTS LOADING AT 2 !
	ISZ	50	/INCREMENT LOAD ADDRESS
	JMP	47	/GO BACK FOR ANOTHER
/
/  SECONDARY BOOT LOADS OVER PRIMARY BOOT UNIT LOCATION 47 IS LOADED,
/  THEN CONTROL PASSES TO SECONDARY BOOT
/
LOAD,	0		/SUBROUTINE TO GIVE AND TAKE DATA FROM CONTROLLER
	STR		/IS HE READY TO TALK TO US?
	JMP XSTRT	/NO, IS HE PERHAPS DONE WITH SILO, OR IN ERROR?
	XDR		/YES, DATA IN OR OUT;IF DATA TO CONTROLLER, AC UNCHANGED
	JMP I	LOAD	/NO MAGIC, JUST EXIT FROM SUBROUTINE
/
/  60 GOES TO OLD SECONDARY BOOT
/  61 HAS DENSITY AND UNIT THAT BOOTED SUCCESSFULLY
/
/
CON420,			/USE IT TO HOLD 420 LITERAL TO START OUT
RX1SAV,	420		/UNIT^20+7004 TO GO TO SYS HANDLER
UNIT,	20		/<DENSITY^400>+<UNIT^20> THAT BOOTED OK
/
	$