1                                	.title	M9312 'CT' BOOT prom for TA11/TU60 controller
       2                                
       3                                	; This source code is an exact copy of the DEC M9312 23-761A9 boot PROM.
       4                                	;
       5                                	; This boot PROM is for the TA11 controller with TU60 drives.
       6                                	;
       7                                	; Multiple units and/or CSR addresses are supported via different entry points.
       8                                	;
       9                                	; Standard devices are 82S131, Am27S13, 74S571 or other compatible bipolar
      10                                	; PROMs with a 512x4 TriState 16pin DIP architecture. This code resides in
      11                                	; the low half of the device; the top half is blank and unused.
      12                                	;
      13                                	; Alternatively, 82S129 compatible 256x4 TriState 16pin DIP devices can be
      14                                	; used, as the uppermost address line (hardwired low) is an active low chip
      15                                	; select (and will be correctly asserted low).
      16                                
      17 177500                         tacsr	=177500				; std TA11 csrbase
      18                                
      19 000000                         tacs	=+0				; control/status
      20 000002                         tadb	=+2				; data buffer
      21                                
      22 165564                         diags	=165564				; console diags phase2 entry
      23                                
      24                                	.asect
      25 173000                         	.=173000
      26                                
      27                                	; --------------------------------------------------
      28                                
      29 173000    124     103          start:	.ascii	"TC"			; device code (reversed)
      30                                
      31 173002 000176                  	.word	last-.			; offset to next boot header
      32                                
      33 173004 000261                  dl0n:	sec				; boot std csr, unit zero, no diags
      34 173006 012700  000000          dl0d:	mov	#0,r0			; boot std csr, unit zero, with diags
      35 173012 012701  177500          dlNr:	mov	#tacsr,r1		; boot std csr, unit <R0>
      36 173016 010704                  dlNb:	mov	pc,r4			; boot csr <R1>, unit <R0>
      37 173020 103042                  	bcc	diag			; br if diags requested
      38 173022 000402                  	br	go			; return to (R4)+2 from diags
      39                                					; then skip over pseudo reboot vector
      40                                
      41                                	; --------------------------------------------------
      42                                
      43 173024 173000                  	.word	173000			; prom start addess @ 24
      44 173026 000340                  	.word	340			; and priority level @ 26
      45                                
      46                                	; --------------------------------------------------
      47                                
      48 173030 010003                  go:	mov	r0,r3			; copy unit number
      49 173032 042703  177776          	bic	#^c1,r3			; mask to 0/1
      50 173036 000303                  	swab	r3			; to high byte
      51 173040 010311                  	mov	r3,(r1)			; to controller<8>
      52                                
      53 173042 010405                  	mov	r4,r5			; r4=r5=173x20
      54 173044 042705  000177          	bic	#177,r5			; r5=173x00
      55 173050 062705  000132          	add	#table-start,r5		; offset to table start
      56 173054 012702  000375          	mov	#375,r2			; -2 as a byte
      57 173060 112503                  	movb	(r5)+,r3		; R3=240
      58                                
      59 173062 112511                  2$:	movb	(r5)+,(r1)		; send 037,015,005,024,224
      60 173064 100407                  	bmi	4$			; exit if last command
      61                                
      62 173066 130311                  3$:	bitb	r3,(r1)			; check trreq<7> or ready<5>
      63 173070 001776                  	beq	3$			; loop if neither
      64                                
      65 173072 105202                  	incb	r2			; count from -2,-1,0,...,177
      66 173074 100772                  	bmi	2$			; loop twice
      67                                
      68 173076 116112  000002          	movb	tadb(r1),(r2)		; write data byte in buffer
      69 173102 000771                  	br	3$			; loop
      70                                
      71 173104 005711                  4$:	tst	(r1)			; check error<15>
      72 173106 100404                  	bmi	5$			; br if error
      73                                
      74 173110 005002                  	clr	r2			; point at address zero
      75 173112 120312                  	cmpb	r3,(r2)			; check for NOP=240 there
      76 173114 001001                  	bne	5$			; br if not, not a boot block
      77                                
      78 173116 005007                  	clr	pc			; jump to bootstrap start
      79                                
      80 173120 000005                  5$:	reset				; reset controller
      81 173122 000164  000002          	jmp	2(r4)			; and retry the boot
      82                                
      83                                	; --------------------------------------------------
      84                                
      85 173126 000137  165564          diag:	jmp	@#diags			; jump to console diags
      86                                
      87                                	; --------------------------------------------------
      88                                
      89 173132    240                  table:	.byte	240			; trreq<7>+ready<5> AND NOP
      90 173133    037                  	.byte	037			; ilbs+rewind+go command
      91 173134    015                  	.byte	015			; spaceforwardblock+go command
      92 173135    005                  	.byte	005			; read+go command
      93 173136    024                  	.byte	024			; ilbs+read command
      94 173137    224                  	.byte	224			; ilbs+read command + 200
      95                                
      96 173140 000000  000000  000000  	.word	0,0,0,0,0,0,0,0		; unused
         173146 000000  000000  000000  
         173154 000000  000000          
      97 173160 000000  000000  000000  	.word	0,0,0,0,0,0,0		;
         173166 000000  000000  000000  
         173174 000000                  
      98                                
      99                                	; --------------------------------------------------
     100                                
     101 173176                         	.=start+176
     102 173176 022763                  crc16:	.word	<022763>		; CRC-16 will go here
     103                                
     104                                last:	; next boot prom starts here
     105                                
     106                                	.end
     106