![]() ![]() 50 Hz or 60 Hz input to both TOD pins is generated from the 9 V AC power input Įxactly, thus any clock delivered is based on the power frequency - and its reliability at point of measurement (*1). set to ONE already flips the second at 50.Set to ZERO lets the counter wrap at 60, while.If it had cared, it could do so by simply handling Bit 7 of CRA (Register 14, $DC0E for CIA1, $DD0E for CIA2). The Kernal is a quick hack, taken straight from the VC20, operating the clock on interrupt base - as alwasy since PET times (as explained on another question about the 6526). It doesn't, as the Kernal doesn't care about the built-in TOD. How does the C64 get an accurate TOD clock on 50 Hz power? ![]() Were there any other components of the C64 that might also beĪffected by the 50 Hz vs.TOD clock is accurate only with PEEK/POKE or machine language? Did C64 BASIC use one of the TOD clocks, or can one check if the.Include these here since the answers are likely to be turned up during Here are some related questions for even further bonus points. In other words: Vice seems to ignore bit 7 of $dc0e TOD Clock as 60Hz clocked and it will always be counting correctĭespite of this. When running this in Vice, it will always end up detecting the Vice Screen cycles against a TOD clock set for 60 Hz input in order toįigure out what the actual input should be. TOD clock on all platforms" which explains how to count For example, Codebase 64's has an article "Initializing One to use?) How did third-party programs that relied on the TOD clockīonus points if you can give the implications of all this for popularĮmulators. Western Japan and other 60 Hz regions? (And did the software set theīit for both CIAs, or was there one that was considered the standard Hz, causing the TOD clock to run 17% slow outside of North America, Have any facilities to set TODIN, or was that just always set to 60 Japan, where consumers might have either 50 Hz or 60 Hz mainsĭid the Commodore-supplied software (Kernal, BASIC, other programs) Via a step-down transformer), but the NTSC C64 was also sold in Hz mains power region (using that region's external power supply or ![]() Not only might someone run a PAL C64 in a 60 It doesn't seem possible to conclusively tell whether the input isĪctually 50 Hz or 60 Hz. Input, though it still says just "60 Hz" at the U1 input.) (The schematic for a newer version of theīoard on page 32 does say "50 Hz OR 60 Hz" at the AND gate output/U2 Mains power is 50 Hz, since as far as I know the external power supplyĪlways generated unregulated 9 V AC from the from the region's AC Signal, this will surely be 50 Hz in regions of the world where AC Though the schematic on page 21 claims that this is a 60 Hz Input to both TOD pins is generated from the 9 V AC power inputĬonverted to a TTL signal using one of the AND gates of a 74LS08 Register A) to 0 for 60 Hz or 1 for 50 Hz.Īccording to the C64/C64C Service Manual, 50 Hz or 60 Hz The CIA is selected via programming bit 7 (TODIN) of CRA (Control Input to the TOD pin (pin 19) the clock input frequency assumed by These calculate time based on a 60 Hz or 50 Hz The C64 has two Time of Day (TOD) clocks, one in each of its 6526 CIAĬhips U1 and U2. ![]()
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