Close by Naming How This Series Completes the Maskrom Picture

# Close by Naming How This Series Completes the Mask-ROM Picture

## 1. Name What Each of the Three Series Actually Covers

Three series now cover mask-programmed read-only memory on this site, each from a genuinely different, non-duplicating angle. `microprocessor_1971_step06` covers the fixed-at-fabrication mechanism itself — a bit embodied by the presence or absence of a fabricated connection — and the 4001's specific role as the 4004's program store, with its own direct comparison against DRAM's 1T1C cell. `eprom_eeprom_history_step08` and `step10` cover mask ROM's real commercial position against EPROM — the plain plastic package and absent program/erase circuitry that made it the cheaper choice once a product's firmware was finalized for volume shipment. This series, `mask_rom_addressing`, covers neither of those: it covers how an address actually gets turned into a row of fixed bits inside the device itself (the diode-matrix and transistor-matrix schemes, contrasted architecturally against DRAM's RAS/CAS and SRAM's word-line/bit-line addressing), the real photomask design-and-fabrication economics that made a mask-ROM bit pattern a genuine, weeks-long commitment, and three named applications — character-generator ROMs, game-cartridge ROMs, and microcode ROM — that have nothing to do with the 4001's own user-facing program-storage role.

## 2. Leave the Picture Complete, Without Forcing a Further Handoff

No further named handoff is forced here, because none of this series' own content leaves a genuine open thread toward a specific next series the way, for example, Mesa Production's exposed-junction cliffhanger genuinely led into Planar Process. The diode-matrix and transistor-matrix addressing schemes, the mask-set lead-time and respin economics, and the character-generator, game-cartridge, and microcode-ROM applications are each closed, self-contained stories told in full within this series' own fourteen steps. Where a genuine connection exists — to `microprocessor_1971_step06`'s fixed-bit mechanism, to `eprom_eeprom_history_step08`/`step10`'s commercial-niche comparison, or to the DRAM and SRAM series' own addressing schemes — it has been named at the point the connection was real, and never retold.

Mask-programmed read-only memory, across these three series taken together, is now covered from its physical mechanism, through its commercial economics, through its internal addressing architecture, to the full range of what it was actually used to store.