TITLE Einstein Silicon Disc GAL 2 PATTERN A REVISION 1.0 AUTHOR TONY BREWER COMPANY - DATE 6/5/13 CHIP ESD2 GAL16V8 R6 R5 R4 R3 DRW DD1 DD2 MREQ IORQ GND M1 WR RD RAS CAS AS1 AS2 SYSCLK RFSH VCC EQUATIONS /RAS = /DRW * /R6 * /R5 * /R4 * /R3 ;Data read/write for first 256kB (R6-R3=0000) + /MREQ * /RFSH ;Refresh, CAS-before-RAS /CAS = /DD2 * /R6 * /R5 * /R4 * /R3 ;Data read/write for first 256kB (R6-R3=0000) + /RFSH ;Refresh, CAS-before-RAS /AS1 = DD1 ;Address strobe 1 for DRAM A0-A7 row address /AS2 = /DD1 ;Address strobe 2 for DRAM A0-A7 column address ; DD1 is DRW delayed (by 74x04 inverter and RC delay) ; DD2 is DD1 delayed (by 74x04 inverter and RC delay) ; ; A 512KB Silicon Disc is possible by connecting two 256KB PCBs, ; with a modified GAL 2 on one of the boards with R6-R3=0001 ; ; More than 512KB is also feasible, but the current version ; of the ROM (v1.1) only supports a 256KB Silicon Disc