; 2022-04-17
; First draft conversion of original equations
; into a hopefully clearer form.
;
; Not tested yet.
;
; Pure combinatorial logic.
; Could be done in a PAL20L10.
;
; Will need testing by comparing the outputs 
; of the two methods.
;
; MINI CORTEX GLUE LOGIC 
CHIP GLUE G22V10 
/MEMEN			=1
/WE			=2
/DBIN			=3
/is_00xx_or_FExx	=4
RA15			=5
AB7			=6
AB6			=7
/ROMEN			=8
/CRUCLK			=9
USER			=10
PROTECT			=11

/CSW		=14
/CSR		=15
/FLAGSEL	=16
WAIT		=17
/9902SEL	=18
/PWE		=19
/MAPSEL		=20
/CFSEL		=21
/RAMSEL		=22
/ROMSEL		=23

EQUATIONS

; aliases

write		= we
read		= dbin

; Intermediate terms:

is_00xx		=	is_00xx_or_FExx	*	/ra15	; in lower 32k
is_FExx		=	is_00xx_or_FExx	*	 ra15	; in upper 32k
;
9902_space	=	is_00xx	*	/ab7	*	/ab6	; 0000
FLAG_space	=	is_00xx	*	/ab7	*	 ab6	; 0040
CF_space	=	is_FExx	*	/ab7	*	/ab6	; FE00
MAP_space	=	is_FExx	*	/ab7	*	 ab6	; FE40
CS_space	=	is_FExx	*	 ab7	*	/ab6	; FE80



; pin definitions
	
ROMSEL	=	memen	*	 romen	*	/ra15	; in lower 32k if enabled

RAMSEL	=	memen	*	/romen	*	/ra15	; in lower 32k if ROM disabled
	or	memen	*	/romen	*	 ra15	; in upper 32k 	
	or	memen	*	/romen	*	we	*	/is_00xx_or_FExx	; exclude writing to "io hole"

FLAGSEL	=	cruclk	*	FLAG_space
9902SEL	=	/memen	*	9902_space	* /user
CFSEL	=	memen	*	CF_space	* /user
MAPSEL	=	memen	*	MAP_space	* /user
CSW	=	memen	*	CS_space	* /user	*	write
CSR	=	memen	*	CS_space	* /user	*	read

PWE	=	we	*	PROTECT	
	or	/MAPSEL

WAIT	=	ROMSEL
	or	CFSEL