A project log for Custom circuit testing using Intel HEX files

Download / upload memory contents into computer motherboards or other devices for test or debugging (using 3 micro-coded controllers)

zpekiczpekic 12/08/2021 at 05:030 Comments

For this project I used a cool little 8085-based single board computer (8085 Minimax) described and graciously provided to me by Ken Yap (thanks again!). I was actually in the process of soldering together the board, and decided to use a verification step before plugging in my vintage Soviet CPU to see if there will even be a chance for it working or not...

 The hardware setup is simple but a bit messy affair:

Few notes:

This is how these connections look in VHDL (top file of the project):

                --PMOD interface
                JA1: inout std_logic;    -- Connected to USB2UART
                JA2: inout std_logic;    -- Connected to USB2UART
                JA3: inout std_logic;    -- Connected to USB2UART
                JA4: inout std_logic;    -- Connected to USB2UART
                JB1: out std_logic;    -- GRAY 74F573.19 A0
                JB2: out std_logic;    -- GRAY 74F573.18 A1
                JB3: out std_logic;    -- GRAY 74F573.17 A2
                JB4: out std_logic;    -- GRAY 74F573.16 A3
                JB7: out std_logic;    -- GRAY 74F573.15 A4
                JB8: out std_logic;    -- GRAY 74F573.14 A5
                JB9: out std_logic;    -- GRAY 74F573.13 A6
                JB10: out std_logic;    -- GRAY 74F573.12 A7
                JC1: out std_logic;    -- WHITE 8085.21    A8
                JC2: out std_logic;    -- WHITE 8085.22    A9
                JC3: out std_logic;    -- WHITE 8085.23    A10
                JC4: out std_logic;    -- WHITE 8085.24    A11
                JC7: out std_logic;    -- WHITE 8085.25    A12
                JC8: out std_logic;    -- WHITE 8085.26    A13
                JC9: out std_logic;    -- WHITE 8085.27    A14
                JC10: out std_logic;    -- WHITE 8085.28    A15
                JD1: out std_logic;    -- PURPLE 8085.30 IO/M (low for memory access)
                -- breadboard signal connections
                BB1: inout std_logic;    -- BLUE 8085.12 AD0
                BB2: inout std_logic;    -- BLUE 8085.13 AD1
                BB3: inout std_logic;    -- BLUE 8085.14 AD2
                BB4: inout std_logic;    -- BLUE 8085.15 AD3
                BB5: inout std_logic;    -- BLUE 8085.16 AD4
                BB6: inout std_logic;    -- BLUE 8085.17 AD5
                BB7: inout std_logic;    -- BLUE 8085.18 AD6
                BB8: inout std_logic;    -- BLUE 8085.19 AD7
                BB9: out std_logic;        -- ORANGE    8085.31 nWR
                BB10: out std_logic;        -- YELLOW    8085.32 nRD