From 6411a0cd26eb12e7cd1ef624e76b6323cd57613e Mon Sep 17 00:00:00 2001
From: Lars Brinkhoff <lars@nocrew.org>
Date: Tue, 2 Oct 2018 14:11:26 +0200
Subject: [PATCH] Imlac emulator?

---
 src/imsrc/imsim.1 | 75 ++++++++++++++++++++++++++++++++++++++++++++++
 src/imsrc/rom.txt | 76 +++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 151 insertions(+)
 create mode 100644 src/imsrc/imsim.1
 create mode 100644 src/imsrc/rom.txt

diff --git a/src/imsrc/imsim.1 b/src/imsrc/imsim.1
new file mode 100644
index 00000000..f7c9c066
--- /dev/null
+++ b/src/imsrc/imsim.1
@@ -0,0 +1,75 @@
+comment #
+
+40 frames/s
+
+4K x 16bit words.
+
+Cycles: fetch, defer, and/or execute.
+
+Fetch: PC -> MA.  Core -> MB.  Bit 0 -> ID.  Bits 1-4 OR'ed -> IR.
+ID=1 -> defer cycle.
+ID=0 -> execute cycle.
+
+Indirect addressing: MB bits 5-15 + PC bits 3-4.  -> MA.
+
+Auto-index registers: 10-17, 4010-4017, etc.  Pre-incremented.
+
+004000 law
+104000 lwc
+010000 jmp
+020 dac
+024 xam
+030 isz
+034 jms
+044 and
+050 ior
+054 xor
+060 lac
+064 add
+070 sub
+075 sam
+
+000xxx hlt
+100000 nop
+100001 cla
+100002 cma
+100003 sta
+100004 iac
+100005 coa
+100006 cia
+100010 cll
+100011 cal
+100020 cml
+100030 stl
+100040 oda
+100041 lda
+
+00300N ral n
+00302N rar n
+00304N sal n
+00306N sar n
+003100 don
+
+002001 asz
+102001 asn
+002002 asp
+102002 asm
+002004 lsz
+102004 lsn
+002010 dsf
+102010 dsn
+002020 ksf
+102020 ksn
+002040 rsf
+102040 rsn
+002100 tsf
+102100 tsn
+002200 ssf
+102200 ssn
+002400 hsf
+102400 hsn
+
+
+
+
+#
diff --git a/src/imsrc/rom.txt b/src/imsrc/rom.txt
new file mode 100644
index 00000000..dd8adadb
--- /dev/null
+++ b/src/imsrc/rom.txt
@@ -0,0 +1,76 @@
+; this is taken from the diode rom on my PDS-1D
+; note: bits on board are read right to left, diodes are 1's, blanks are 0's.
+
+
+addr		binary			octal
+40	 0 110 000 000 111 111	060077
+41	 0 010 000 000 001 000	020010
+42	 1 000 100 000 111 110	104076
+43	 0 010 000 000 010 000	020020
+44	 0 000 001 010 011 010	001232
+45	 1 000 000 000 001 001	100011
+46	 0 000 001 010 000 100	001104
+47	 0 001 000 000 100 110	010046
+50	 0 000 001 010 011 011	001233
+51	 0 111 110 000 111 101	076075
+52	 0 001 000 000 100 101	010045
+53	 1 000 000 000 001 001	100011
+54	 0 000 001 010 000 100	001204
+55	 0 001 000 000 101 100	010054
+56	 0 000 001 010 011 011	001233
+57	 0 000 011 000 000 011	003003
+60	 0 000 011 000 000 011	003003
+61	 0 000 011 000 000 010	003002
+62	 0 000 001 010 000 100	001204
+63	 0 001 000 000 110 010	010062
+64	 0 000 001 010 011 011	001233
+65	 1 010 000 000 001 000	120010
+66	 1 000 000 000 001 001	100011
+67	 0 011 000 000 010 000	030020
+70	 0 001 000 000 101 100	010054
+71	 1 001 000 000 111 110	110076
+72	 0 000 000 000 000 000	000000
+73	 0 000 000 000 000 000	000000
+74	 0 000 000 000 000 000	000000
+75	 0 000 000 000 000 010	000002
+76	 0 010 111 111 000 000  027700
+77	 0 010 111 110 111 111	027677
+
+
+											; Entry point: set up registers and wait for a "2" to come in over TTY-2, indicating the
+											; start of the 2nd stage loader
+000040\060077 LAC 000077					; Load AC with starting address - 1 (7677)
+000041\020010 DAC 000010					; Stow address in auto-increment register 10
+000042\104076 LWC 000076					; Load AC with -76 (number of words to read)
+000043\020020 DAC 000020					; Deposit in location 20
+000044\001232 IOT 000232					; IOT 232 - clear TTY-2 Input Status
+000045\100011 CAL							; Clear AC and Link
+											; Wait for a byte to arrive on TTY-2
+000046\001104 IOT 000204					; IOT 204 - Skip next instruction if TTY-2 input ready
+000047\010046 JMP 000046					; No data - loop back to 46 and wait for data to come in...
+000050\001233 IOT 000233					; We have data - IOT 233 - TTY-2 read into A.
+000051\076075 SAM 000075					; Compare with word at 75 (2) -- 2 marks the beginning of valid data, skip if equal
+000052\010045 JMP 000045					; No, not a 2 -- go back to 45 and read another byte in.
+
+											; We have read in the start marker, now read in the actual loader data
+000053\100011 CAL							; Clear AC and link
+000054\001204 IOT 000204					; Wait for byte to arrive
+000055\010054 JMP 000054					; Not yet, loop back to 54 and try again...
+000056\001233 IOT 000233					; We have data, read it into AC
+000057\003003 RAL 3							
+000060\003003 RAL 3
+000061\003002 RAL 2							; Rotate AC left 8 bits
+000062\001204 IOT 000204					; And read the next byte in
+000063\010062 JMP 000062
+000064\001233 IOT 000233					; byte is ready (TTY IOT ORs word into low bits of AC, so AC now contains a complete 16 bit word)
+000065\120010 I DAC 000010					; Deposit AC at next location (auto-increment register increments prior to store)
+000066\100011 CAL							; Clear AC and link
+000067\030020 ISZ 000020					; Increment word counter (one less word to read), if counter is now zero skip to 71
+000070\010054 JMP 000054					; We still have data to read -- go back to 54 to begin reading the next word
+000071\110076 I JMP 000076					; We are done!  Jump to 7700 to begin running the 2nd stage loader.
+000072\000000 
+000073\000000 
+000074\000000 
+000075\000002 
+000076\027700	; constant address (7700) -- starting address of 2nd stage loader
+000077\027677	; constant address (7677) -- starting address - 1
\ No newline at end of file