# 16V8 for Rack8 Real Memory

Device 16V8

input
    A11:11,	   #Address bits from 8008
    A12:9,
    A13:8, 
    Lowram:1,      # True if we want RAM in the low 2K, False to get EPROM
    Midram:2,      # True if we want RAM for the next 4K and banks, False to get EPROM
    Lowapl:3,      # True to have APL in the first 2K, False to have Loader in
                   #  the first 2K. Used only if we want EPROM in the low 2K,
                   #   that is, if lowram is False.
    Pint:6,        # True if we are processing an interrupt
    Mer.L:4,       # True if the CPU is doing a memory read
    Mew.L:5,       # True if the CPU is doing a memory write
    SS_Read.L:7,   # True if the SelfScan is doing a memory read
    AltWs:14,      # True if we want to use the alternate workspace

output
    Ea_Low_SS:12,  # High if EA_Low is from the SelfScan, Low if from the CPU
    Ea_High_0:16,  # These two select the EA high: 00 bank, 01 Normal, 10 Low,  11 SelfScan
    Ea_High_1:15,
    E_read.L:17,   # True if we are reading from eprom
    R_sel.L:19,    # True if we are reading or writing ram
    R_write.L:18,  # True if we are writing ram
    Ea_14Norm:13,  # The EA14 line when in normal mode. This is for implementing
                   #   the alternate workspace

temp
    low,          # True if accessing low 2K          0000-07FF
    mid,          # True if accessing 4K above low 2K 0800-17FF
    bank,         # True if accessing bank area       1800-1FFF
    workspace,    # True if accessing workspace       2000-7FFF
    ram,          # True if accessing RAM
    eprom,        # True if accessing EPROM
    EA_SS,	  # True if we are accessing memory for the SelfScan
    EA_Normal,    # True if we are doing a normal access: not bank, not loader, not SelfScan
    EA_Loader,    # True if we are accessing the loader

implementation

low        equ !A13 & !A12 & !A11
mid        equ !A13 & ((!A12 & A11) | (A12 & !A11))
bank       equ !A13 & A12 & A11
workspace  equ A13
EA_SS      equ SS_Read
EA_Loader  equ low & !LowRam & !LowApl
EA_Normal  equ !Bank & !EA_Loader & !EA_SS

#Low EA comes from the CPU unless we are reading for the SS
Ea_Low_SS  equ EA_SS

Ea_High_0  equ EA_Normal | EA_SS
Ea_High_1  equ EA_Loader | EA_SS

ram      equ !pint & ((low & lowram)  | ((mid | bank) & Midram) | workspace)
eprom    equ !pint & ((low & !lowram) | ((mid | bank) & !Midram))

e_read   equ mer & eprom
r_sel    equ (((mer & !pint) | mew) & ram) | (SS_Read & !pint)
r_write  equ mew & ram

#Make Ea_14Norm high if we are accessing RAM and we want the alternate workspace
Ea_14Norm equ ram & AltWs