Editing Commodore 64 (section)

==== Input/output (I/O) ports and power supply ====
[[File:Commodore-64-Computer-BL.jpg|thumb|right|upright=1.4|Commodore 64 ports (from left: Joy1, Joy2, Power switch and jack, ROM cartridge, RF-adj, RF modulator, A/V, Serial 488 bus, Tape, User)]]
* I/O ports:<ref name="computermuseum_li-Commodore64-Back">{{cite web|title=empty|url=http://www.computermuseum.li/Testpage/Commodore64-Back.jpg|url-status=dead|archive-url=https://web.archive.org/web/20100216022431/http://www.computermuseum.li/Testpage/Commodore64-Back.jpg|archive-date=February 16, 2010}} 090505 computermuseum.li</ref>{{better source needed|reason=This is just an image with no supporting information, e.g. provenance and to confirm it's actually a C64|date=August 2021}}
** [[ROM cartridge]] expansion slot (44-pin slot for [[edge connector]] with 6510 CPU address/data bus lines and control signals, as well as GND and voltage pins;<ref>{{cite web|url=http://www.hardwarebook.info/C64_Cartridge_Expansion|title=The Hardware Book|access-date=November 17, 2014}}</ref> used for program modules and memory expansions, among others)
** Integrated [[RF modulator]] television antenna output via an [[RCA connector]]. The used channel could be adjusted from number 36 with the [[potentiometer]] to the left.
** 8-pin [[DIN connector]] containing [[composite video]] output, separate [[S-Video|Y/C]] outputs and sound input/output. This is a 262° horseshoe version of the plug, rather than the 270° circular version. Early C64 units (with motherboard Assy 326298) use a 5-pin DIN connector that carries composite video and luminance signals, but lacks a chroma signal.<ref name="Carlsen">{{cite web|url=http://project64.c64.org/hw/avconnect.txt|title=C64 video port|last=Carlsen|first=Ray|access-date=September 13, 2008|archive-date=June 29, 2018|archive-url=https://web.archive.org/web/20180629085250/http://project64.c64.org/hw/avconnect.txt|url-status=dead}}</ref>
** [[Commodore bus|Serial bus]] (proprietary serial version of [[IEEE-488]], 6-pin DIN plug) for CBM printers and disk drives
** [[Commodore PET|PET]]-type [[Commodore Datasette]] 300 [[baud]] tape interface (edge connector with digital cassette motor/read/write/key-sense signals), Ground and +5V DC lines. The cassette motor is controlled by a +5V DC signal from the 6510 CPU. The 9V AC input is transformed into unregulated 6.36V DC<ref name="zimmers_250469-rev_A-right">{{cite web|title=250469 rev.A right|url=http://www.zimmers.net/anonftp/pub/cbm/schematics/computers/c64/250469-rev.A-right.gif}} 100610 zimmers.net</ref> which is used to actually power the cassette motor.<ref name="zimmers_250469-rev_A-left">{{cite web|title=250469 rev.A left|url=http://www.zimmers.net/anonftp/pub/cbm/schematics/computers/c64/250469-rev.A-left.gif}} 100610 zimmers.net</ref>
** User port (edge connector with [[Transistor-transistor logic|TTL]]-level signals, for modems and so on; byte-parallel signals which can be used to drive third-party parallel printers, among other things, 17 logic signals, 7 Ground and voltage pins, including 9V AC)
** 2 × screwless [[D-subminiature|DE9M]] [[game controller]] ports ([[Atari joystick port|compatible with Atari 2600 controllers]]), each supporting five digital inputs and two analog inputs. Available peripherals included digital [[joystick]]s, analog [[paddle (game controller)|paddles]], a [[light pen]], the Commodore [[Commodore 1351|1351 mouse]], and graphics tablets such as the [[KoalaPad]].
* Power supply:
** 5[[Volt|V]] [[Direct current|DC]] and 9V [[Alternating current|AC]] from an external "power brick", attached to a 7-pin female DIN-connector on the computer.<ref name="allpinouts_org-Commodore_C64_Power_Supply">{{cite web|url=http://www.allpinouts.org/index.php/Commodore_C64_Power_Supply|title=Commodore C64 Power Supply Connector Pinout – AllPinouts}} 090505 allpinouts.org</ref>

The {{nowrap|9 volt AC}} is used to supply power via a [[charge pump]] to the SID sound generator chip, provide {{nowrap|6.8V}} via a rectifier to the cassette motor, a "0" pulse for every positive half wave to the time-of-day (TOD) input on the CIA chips, and {{nowrap|9 volts AC}} directly to the user-port. Thus, as a minimum, a {{nowrap|12 V}} [[Square wave (waveform)|square wave]] is required. But a {{nowrap|9 V}} [[sine wave]] is preferred.<ref name="zimmers_net-250469-rev_A-left">{{cite web|title=Commodore-64 BN/E 250469 schematic (left)|url=http://www.zimmers.net/anonftp/pub/cbm/schematics/computers/c64/250469-rev.A-left.gif}} 090519 zimmers.net</ref><ref name="zimmers_net-250469-rev_A-right">{{cite web |title=Commodore-64 BN/E 250469 schematic (right)|url=http://www.zimmers.net/anonftp/pub/cbm/schematics/computers/c64/250469-rev.A-right.gif}} 090519 zimmers.net</ref>{{better source needed|reason=These are just images, with no supporting information especially provenance|date=August 2021}}