paged-rom-ram-1mb

paged 1 MB SRAM/512K flash

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ReferencesQtyDescriptionManufacturerMPNDigikeyMouserLCSC
C1, C2, C3, C4, C5, C6, C7, C880.1 µF 0603 capacitorSamsungCL10B104KB8NNNC1276-1000-1-ND187-CL10B104KB8NNNCC1591
J11right-angle pin header, 1x39, .100""SamtecTSW-139-08-L-S-RASAM1043-39-ND
R1, R2, R3, R444.7kΩ 0603 resistorYageoRC0603FR-074K7L311-4.70KHRCT-ND603-RC0603FR-074K7LC99782
R5, R6, R7, R841kΩ 0603 resistorYageoRC0603FR-071KL311-1.00KHRCT-ND603-RC0603FR-071KLC22548
Socket_U11PLCC-32 socket, through-holeAdam TechPLCC-32-AT2057-PLCC-32-AT-NDC3170448
U11512Kx8 flash memoryMicrochipSST39SF040-55-4C-NHE-TSST39SF040-55-4C-NHE-TCT-ND579-39SF040554CNHETC632846
U2, U32512Kx8 SRAMAlliance MemoryAS6C4008-55SIN1450-1028-ND913-AS6C4008-55SINC1350086

rc2014-compat

A respin of the RC2014 ecosystem. I don't have any opposition to building things out of SMD parts (in some ways, I find it easier to work with), so some boards might go that way to the extent that parts availability allows. Also, I'd like to keep all board sizes within the 100x100mm limit within which PCB fabs offer their cheapest rates (like $2 double-sided at JLCPCB, for instance).

paged-ram-rom-1mb

This started out as a copy of the schematic from the RC2014 GitHub. I brought it into KiCad 6, replaced the "rescued" symbols from the original with more current ones in the KiCad library, redid the connections in what I think is an easier-to-follow style (global labels instead of buses), and re-did the PCB layout from scratch (since that wasn't included). I also swapped out SMDs for through-hole parts.

This freed up enough space to add a second SRAM chip. Banks 0-31 select ROM (flash) and banks 32-95 (previously 32-63) select RAM. 16K chunks of either ROM or RAM can be paged into any of four slots in the memory map: $0000-$3FFF, $4000-$7FFF, $8000-$BFFF, $C000-$FFFF. Reset maps ROM page 0 into all slots.