schematic.txt

Please use a 30-pin simm module socket! module pins connected to Arduino mega pins as detailed below :


30-pin SIMM Memory Module
Pin #	  Name  Signal Description    Arduino Mega Pin
1	      VCC   +5 VDC
2	      /CAS  Column Address Strobe		
3	      DQ0   Data 0				        49
4	      A0    Address 0	            22
5	      A1    Address 1	            23
6	      DQ1   Data 1	              48 
7	      A2    Address 2	            24
8	      A3    Address 3	            25
9	      VSS   Ground				        
10	    DQ2   Data 2	              47
11	    A4    Address 4	            26
12	    A5	  Address 5	            27
13	    DQ3   Data 3	              46
14	    A6	  Address 6	            28
15	    A7	  Address 7	            29
16	    DQ4	  Data 4                45
17	    A8	  Address 8             37
18	    A9	  Address 9             36
19	    A10	  Address 10            35
20	    DQ5	  Data 5                44
21	    /WE	  Write Enable	
22	    VSS	  Ground				
23	    DQ6	  Data 6                43
24	    A11	  Address 11            34
25	    DQ7	  Data 7                42
26	    QP	  Data parity out			
27      /RAS  Row Address Strobe
28	    /CASP	CAS Parity Strobe	
29      DP    Data parity in			
30	    VCC   +5 VDC


30-pin SIMM Memory Module		Arduino
Address pin 0 to 5 (A0..A5)		PORTB (digital pin 8..13)
Address pin 6 to 11 (A6..A11)		GND
Data pin 0 to 7 (DQ0..DQ7)		PORTD (digital pin 7..0) (in that order, DQ0-pin7, DQ1-pin6, DQ2-pin5...DQ7-pin0)
The others will be not connected.


This way you will address 6 bits for rows and 6 bits for columns.
Addresses space will be of 64rows x 64columns = 4096 addresses
1 byte each = 4KB of space.

If you need to use more RAM you can solder the 3 analog pins remaining
to simm ram module pins A6, A7 and A8. It will give you 256 KB of RAM space.