{"id":1018,"date":"2019-03-19T12:40:35","date_gmt":"2019-03-19T19:40:35","guid":{"rendered":"https:\/\/www.pagetable.com\/?p=1018"},"modified":"2019-03-19T12:40:35","modified_gmt":"2019-03-19T19:40:35","slug":"commodore-peripheral-bus-overview","status":"publish","type":"post","link":"https:\/\/www.pagetable.com\/?p=1018","title":{"rendered":"Commodore Peripheral Bus: Overview"},"content":{"rendered":"

The well-known Serial Bus (aka Serial “IEC” Bus) of the Commodore 64 that connects to disk drives such as the 1541 is just one variant of a whole family of busses and protocols used by the line of 8 bit Commodore machines from the PET to the C65. This is the first article of a multi-part series<\/strong> on the Commodore Peripheral Bus family<\/strong>.<\/p>\n

The following figure compares the different protocol stacks. There are three different connectors with their unique byte transfer protocols: IEEE-488, Serial, and TCBM. Fast Serial and JiffyDOS are optimized, but backwards-compatible protocols for existing cables, and CBDOS integrates the drive directly into the computer. The higher level protocols are the same across all Commodore 8 bit machines, including the “KERNAL” operating system APIs.<\/p>\n

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These are the properties and tradeoffs of the different variants of the protocol stack1<\/a><\/sup>:<\/p>\n\n\n\n\n\n\n\n\n
<\/th>\n IEEE-488 <\/th>\n Serial <\/th>\n Fast Serial <\/th>\n JiffyDOS <\/th>\n TCBM <\/th>\n CBDOS <\/th>\n<\/tr>\n<\/thead>\n
Data Wires <\/td>\n 13 <\/td>\n 3 <\/td>\n 4 <\/td>\n 3 <\/td>\n 12 <\/td>\n – <\/td>\n<\/tr>\n
Speed (KB\/sec) <\/td>\n 2.1 <\/td>\n 0.4 <\/td>\n 2.1 <\/td>\n 2.1 <\/td>\n 2.4 <\/td>\n ∞ <\/td>\n<\/tr>\n
Controller Code (bytes) <\/td>\n 334 <\/td>\n 434 <\/td>\n 708 <\/td>\n 739 <\/td>\n 262 <\/td>\n 0 <\/td>\n<\/tr>\n
Comments <\/td>\n compatible with industry standard <\/td>\n very slow <\/td>\n requires decidated bit shifting hardware <\/td>\n <\/td>\n point-to-point <\/td>\ndrive integrated into computer <\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

All variants are based on the IEEE-488 standard and therefore share (mostly) the same basic architecture:
\n* All participants are daisy-chained<\/strong>.
\n* One dedicated controller<\/strong> (the computer) does bus arbitration of up to 31 devices<\/strong>.
\n* One-to-many<\/strong>: Any participant can send data to any set of participants.
\n* A device has multiple channels<\/strong> for different functions.
\n* Data transmission is byte stream<\/strong> based.<\/p>\n

The different variants and layers will be described in multiple articles.<\/p>\n\n

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NOTE:<\/em><\/strong> I am releasing one part every week, at which time links will be added to the bullet points below. The articles will also be announced on my Twitter account @pagetable<\/a> and my Mastodon account @pagetable@mastodon.social<\/a>.<\/p>\n<\/blockquote>\n\n