Simple 16Bit Accumulator Computer
author Neil Franklin, last modification 2000.08.27

Memory Space

64k Addresses = 32Pages*2kWords*16Bits

Register Set

A	Accumulator
I	Instruction Pointer (Load=Jump)
B0	ev. Address Base 0
B1	"                1

Instruction Set

	OOOOIAAAAAAAAAAA
OOOO=D	    SSSSDDDDFFFF
OOOO=E	    ICCCCCCCCCCC
OOOO=F	    I???????????

	OOOO			Operation Code
				  0=ORA/1=AND/2=XOR/3=TST A = A OOOO Mem(Addr)
				  4=ADD/5=SUB/6=???/7=CMP A = A OOOO Mem(Addr)
				  8=LDA, A = Mem(Addr)
				  9=STA, Mem(Addr) = A
				  A=JMP, I = Addr
				  B=JSR, A = I, I = Addr
			  	  C=JAZ (Jump Acc Zero), I = Addr if A = 0
				  D=IOT? (In Out Transfer)
				  E=LAI? (Load Acc Immediate), A = Const
				  F=OOR (Operate On Registers)
	    I			Indirect, use Mem(Addr) for Addr
	     AAAAAAAAAAA	Direct Address 2kWords
	     I?			Addit Addr modes post-incr/pre-decr Mem(Addr)
	      I?		Addit Addr mode for Immediate
	       BB?		Address Base 0=zero-rel/1=I-rel
				  or 0=I-rel/1=B-rel
                		  or additional 10=B0-rel, 11=B1-rel
	    SSSS		SlotID=0..F, F=CPU
		CCC		Chip on card=0..7
		   FFFFF	Function on Chip=0..1F
		TT?		IO cycle type information
	    I			Invert Const before loading
	     CCCCCCCCCCC	Constant to be loaded
	    I			Invert Data to Acc
	     ???????????	cla, shift/rot, etc.


Virtual Memory Management (Table in CPU)

32Pages->512Pages * 2kWords
Table Format: 32Entries*11Bits, bits as:
  15..14 rw, 13..9 software use, 8..0 pageno


Suggested Memory Layout (RAM only, boot via auto-DMA)

0000..FFFF 64kWords Data/Prog/OS RAM


Suggested Memory Layout (with ROMs)

0000..7FFF 32kWords Data/Prog/OS RAM
8000..BFFF 16kWords Data/Prog/OS RAM or Prog/OS ROM
C000..EFFF 12kWords Data/Prog/OS RAM or Prog/OS ROM
Fs00..FsFF 16Slots*256Words OS/Driver ROMs [s=SlotID=0..F, F=CPU]