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oldben
Joined: Mon Oct 07, 2019 2:41 am
Posts: 859
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I have compacted the 20 bit cpu, to 16 bits. MMU's are a PTA, but you need split code and data, user and system. Code: draft JUNE 16 2024
16 BIT segmented CPU.
64Kb user data space, stack
64Kb user program space
64Kb sys data space, sys stack
64kb sys program space
Cpu:
The cpu has a Carry flag and 7 general purpose registers and PC/Z
special registers. ADX is addition that does not affect the carry flag.
ADD/SUB/CAD and shifts affect the carry.
Adressing modes are register indirect:
INDEXED r + #
AUTO (A) -r r% r+
opcode postfix . byte
, unsigned byte
% register
Instruction format:
+-+---+---+---+---+---+
|Q|OOO|AAA|C+#|###|###| 0 # QUICK 7 BITS
+-+---+---+---+---+---+
+-+---+---+---+---+---+
|Q|OOO|AAA|CMM|XXX|?RR| 1 MEMORY REF
+-+---+---+---+---+---+
OPCODE TABLES:
REGISTER
AX RR MODE
Q = 0
CTL,QUICK #
Q = 1
0 A DIRECT JMP/JSR,SCC/JCC
1 B -R LEA/HLT,REG OP,SHIFT
2 C R% OP BYTE ? SIGNED,UNSIGNED
3 D R+ OP WORD ? USER SPACE,SYS SPACE
4 S
5 X
6 Y
7 Z/P
MEMORY REF
OOO OP C
0 ST/STP (EFA) = AAA
(EFA) = AAA PROGRAM SPACE
1 ADD/ADC AAA = AAA + (EFA) + ?0,C
2 SUB/SBC AAA = AAA + ~(EFA) + ?1,C
3 CAD/CAC AAA = ~AAA + (EFA) + ?1,C
4 LD/ AAA = (EFA)
LDP AAA = (EFA) PROGRAM SPACE
5 OR/ AAA = AAA | (EFA)
EQV AAA = AAA XNOR (EFA)
6 AND AAA = AAA & (EFA)
XOR AAA = AAA ^ (EFA)
7 ADX AAA = AAA + (EFA)
ATX AAA = AAA + (EFA)<<1
micro code 256 x 24
87 654 321
RA:SMM:CCC
01:1PP:CCC PANEL
00:100:CCC DI-EI/QUICK #
1a:smm:CCC NORMAL DECODE
This will be virtual machine for now, but a real cpu seems possible, once I get the micro code defined. One option is to have the carry flag select byte high,low and make atx ac = ac + (efa)>>1 setting carry. This will break C, how ever, but gives you 2x the data/code space.
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| Sun Jun 16, 2024 8:19 am |
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oldben
Joined: Mon Oct 07, 2019 2:41 am
Posts: 859
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Code: draft JUNE 18 2024
16 BIT segmented CPU.
version #1 no segments
Cpu:
The cpu has a Carry flag and 7 general purpose registers and PC/Z
special registers. ADX is addition that does not affect the carry flag.
ADD/SUB/CAD and shifts affect the carry.
Adressing modes are register indirect:
INDEXED r + #
AUTO (A) -r r% r+
CPU 16
+----+----+----+----+
|OOOO:1AAA|?XXX:MMRR| MEMORY
+----+----+----+----+
|OOOO:0AAA|+###|####| BYTE #/NOP
+----+----+----+----+
opcode postfix . byte
, unsigned byte
% register
Instruction format:
ST OP
0 A LEA OP REG
1 B JSR -R JCC -R
2 C JSR R% JCC R%
3 D JSR R+ JCC R+
4 S - SFT
5 X CTL SCC #-1
6 Y CTL -
7 Z/# CTL SCC # 1
8 ST R) OP R) WORD
9 ST -R OP -R WORD
A ST R% OP R% WORD
B ST R+ OP R+ WORD
C ST R) OP R) BYTE ?=UNSIGNED
D ST -R OP -R BYTE ?=UNSIGNED
E ST R% OP R% BYTE ?=UNSIGNED
F ST R+ OP R+ BYTE ?=UNSIGNED
QUICK NOP OP # -128+127
MEMORY REF
OOO OP C
0 ST/STP (EFA) = AAA
(EFA) = AAA PROGRAM SPACE
1 ADD/ADC AAA = AAA + (EFA) + ?0,C
2 SUB/SBC AAA = AAA + ~(EFA) + ?1,C
3 CAD/CAC AAA = ~AAA + (EFA) + ?1,C
4 LD/ AAA = (EFA)
LDP AAA = (EFA) PROGRAM SPACE
5 OR/ AAA = AAA | (EFA)
EQV AAA = AAA XNOR (EFA)
6 AND AAA = AAA & (EFA)
XOR AAA = AAA ^ (EFA)
7 ADX AAA = AAA + (EFA)
ATX AAA = AAA + (EFA)<<1
micro code 256 x 24
87 654 321
RS:MMA:CCC
01:PP0:CCC PANEL
01:001:CCC NOP,TRAP/QUICK #
1S:MMA:CCC NORMAL DECODE
Small C seems to compile. Off to find a bigger C
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| Wed Jun 19, 2024 4:32 am |
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BigEd
Joined: Wed Jan 09, 2013 6:54 pm
Posts: 1852
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> Small C seems to compile
A milestone! Congratulations!
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| Wed Jun 19, 2024 7:08 am |
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oldben
Joined: Mon Oct 07, 2019 2:41 am
Posts: 859
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I now have the simple segmented version working, and small c outputting code (64kb) and (64kb) data segment.
Planned software: Fat table disk format,sub directories,single user. 1977 ish hardware time frame. 16Kb for the OS and 32Kb for user space.
Next month to work on the hardware version.
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| Mon Jul 01, 2024 4:59 am |
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oldben
Joined: Mon Oct 07, 2019 2:41 am
Posts: 859
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Picked up a 68000 SBC, and plan to emulate a 32 bit cpu with18 bit addressing.
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| Fri Jul 12, 2024 8:01 am |
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robfinch
Joined: Sat Feb 02, 2013 9:40 am
Posts: 2407
Location: Canada
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Which SBC?
_________________Robert Finch http://www.finitron.ca
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| Fri Jul 12, 2024 4:49 pm |
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oldben
Joined: Mon Oct 07, 2019 2:41 am
Posts: 859
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robfinch wrote: Which SBC? The one now sent by Snail Mail.  https://www.tindie.com/products/rosco/r ... -full-kit/(You save by having no case, or floppies)
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| Fri Jul 12, 2024 6:05 pm |
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oldben
Joined: Mon Oct 07, 2019 2:41 am
Posts: 859
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Code: draft JULY 12 2024
32 BIT segmented CPU.
version #1 no segments 512 Kb address space.
Cpu:
The cpu has a Carry flag and 8 general purpose registers and PC/Z
special registers. (A,B,C,D) ADD/SUB/CAD and shifts affect the carry.
Adressing modes are register indirect:
INDEXED r + # SHORT
DIRECT # ADR
AUTO r% r+
PSH -r
CPU 32
+----+----+----+----+
|OOOO:UAAA|JSSI:xXXX| MEMORY
+----+----+----+----+
opcode postfix . byte
, unsigned
% register
index
0xxx r%
1xxx r+
0xxx r] ####
1nnn Z ####
±nnn QK
±nnn BR ####
Instruction format:
ST OP JMP
0 A CTL QUICK SCC
1 B LEA REG BCC
2 C B R+ B R+ SFT #X
3 D/# B R] B R] BSR
4 W W R+ W R+ JMP R+
4 X W R] W R] JMP R]
4 Y L R+ L R+ JSR R+
4 S L R] W R] JSR R]
OOO OP C
0 ST/PSH
1 ADD/ADC AAA = AAA + (EFA) + ?0,C
2 SUB/SBC AAA = AAA + ~(EFA) + ?1,C
3 CAD/CAC AAA = ~AAA + (EFA) + ?1,C
4 LD AAA = (EFA)
5 OR AAA = AAA | (EFA)
6 AND AAA = AAA & (EFA)
7 XOR AAA = AAA ^ (EFA)
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| Fri Jul 12, 2024 9:22 pm |
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oldben
Joined: Mon Oct 07, 2019 2:41 am
Posts: 859
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Code: draft JULY 13 2024
32 BIT segmented CPU.
version #2 still no segments, 512Kb
Cpu:
Since this is planed to be emulated on 68000
endian is what ever the 68000 is.
A quick and dirty C emulator is planned.
The cpu has a Carry flag and 8 general purpose registers and PC/Z
special registers.
ADD/SUB/CAD and shifts affect the carry.
Adressing modes are register indirect:
INDEXED r + # SHORT
DIRECT # ADR
AUTO -r r+
CPU 32
+----+----+----+----+
|OOOO:-AAA|JSSI:IXXX| MEMORY
+----+----+----+----+
- reserved
opcode postfix
.R REG
.Q QUICK
.B byte
.W word
.L long
II
0 R+ or #
1 -R
2 Z]
3 R]
SS
0 OTHER
1 .B
2 .W
3 .L
J JUMP
0 OPS
1 SHIFT and CONTROL
index
low
0xxx r+ XXXX high
1xxx -r XXXX
1xxx r] XXXX ####
0nnn Z XXX# ####
±nnn QK XXX#
±nnn BR XXX# ####
Instruction format:
ST OP JMP
0 A CTL QUICK SCC
1 B LEA REG BCC
2 C B R+ B R+ SFT #X
3 D/# B R] B R] BSR
4 W W R+ W R+ JMP R+
4 X W R] W R] JMP R]
4 Y L R+ L R+ JSR R+
4 S L R] W R] JSR R]
OOO OP C
0 ST
1 ADD/ADC AAA = AAA + (EFA) + ?0,C
2 SUB/SBC AAA = AAA + ~(EFA) + ?1,C
3 CAD/CAC AAA = ~AAA + (EFA) + ?1,C
4 LD AAA = (EFA)
5 OR AAA = AAA | (EFA)
6 AND AAA = AAA & (EFA)
7 XOR AAA = AAA ^ (EFA)
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| Sat Jul 13, 2024 10:42 pm |
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