Editing Acorn Atom (section)

== Main board components ==

The IC designators below are from the [[Acorn Atom Technical Manual]] parts list.<ref name="atomtm">[[Acorn Atom Technical Manual]] (Issue 2, October 1980), Acorn Computers &mdash; hosted on this wiki. Source for the IC complement (IC22 6502, IC31 6847, IC25 INS8255, IC26 7445, IC20 MM52164 ROM, IC42/43/51/52 2114 RAM, IC53/IC54 LM340T-5 regulators), the crystals (X1 3.58&nbsp;MHz, X2 4.00&nbsp;MHz), the capacitor list, and the 8&nbsp;V supply with the LK6/LK7 5&nbsp;V conversion.</ref>

{| class="wikitable styled-table" style="width:95%; text-align:center;"
! Component !! Device !! Designator !! Function
|-
| '''CPU''' || MOS 6502 @ 1 MHz || IC22 || Central processor
|-
| '''Video''' || Motorola MC6847 VDG || IC31 || 256×192 graphics / 32×16 text
|-
| '''Peripheral interface''' || INS8255 PPI || IC25 || Keyboard, cassette and loudspeaker I/O
|-
| '''Keyboard row driver''' || 7445 BCD-to-decimal decoder || IC26 || Drives the keyboard matrix rows
|-
| '''VIA (optional)''' || MOS 6522 || (B800) || Printer (Centronics) interface &mdash; fitted only on expanded machines
|-
| '''RAM''' || 2114 static RAM (1K×4) || IC42, IC43, IC51, IC52 (+ expansion) || 2 KB base, expandable to 12 KB
|-
| '''ROM''' || MM52164 mask ROM (base) || IC20 || 8 KB system ROM (MOS + BASIC)
|-
| '''Clocks''' || 4.00 MHz + 3.58 MHz crystals || X2, X1 || CPU clock (÷ to 1 MHz) and MC6847 video timing
|-
| '''Cassette amp''' || LM358 op-amp || IC46 || CUTS read/write circuit
|-
| '''Regulators''' || 2× LM340T-5 (7805) || IC53, IC54 || +5 V regulation, one per board half
|}