Can anyone explain this?

Started Mar 20, 2012 | Discussions thread
Regular MemberPosts: 427Gear list
Re: Didn't work :(
In reply to LUIS A GUEVARA, Apr 6, 2012


I am going to have to start again from scratch because some readers are not understanding or reading the CANON TC schematics :

Here is the Schematic again with RED rectangles and arrows showing the camera side at LEFT , and the Lens side at RIGHT:

You've got it backwards. The lens attaches on the left and the camera on the right.

Notice the schematic shows the round pins on the left, they interface with the contact surfaces on the lens. Conversely the contact surfaces normally found on lenses are shown on the right in the schematic, they interface with the pins in the camera exactly like a lens would.

If you still have a doubt as to what is what , please correlate the parts numbers from the schematic, to the Data sheet here:

At left , camera side , CA1-7777-000 C 1 MOUNT BODY.
At right ,CY1-2561- MOUNT, LENS

I have added colored rectangles to avoid confusion.

It didn't help, your still confused.
See page 15 of this service manual for the Canon D30

That camera uses the exact same part (CA1-7777-000 C 1 MOUNT BODY) as the one shown on the left in the schematic of the TC. It is meant to attach a lens but Canon calls it a body mount.

Remember this is a Canon T.C. schematic , not a Sigma one . The purpose of bring ing it up was to exploit possible similarities between the two brands .

There was no intention to propose the use of a TC to solve the problem . I was only to illustrate some basic concepts pertaining to a NON ARBITRATED Synchronous Serial Communication Bus , such as :

  • The Master / Slave relationship

  • The Passivity of the slave data lines

  • The difference between Hard Coding of pins and Soft Coding of the Data that passes through them

  • Use of Interlock to establish Initialization Priorities of removable devices.

  • The use of Mechanically actuated switches to rapidly & UNAMBIGUOUSLY detect presence of devices , as opposed to repeated , wasteful Polling of lines or pins.

With al that said about the use of a Serial Peripheral Interface Bus as the basis for the CANON EF MOUNT I have to point out that the image that follows is of a Sigma SD1 camera Mirror Cage shown previously only to ask some willing person to look into his MERRILL camera to see if the mechanical switch was also present in that model.

This was confirmed and some tests were performed by willing persons and some conclusions were derived from them. The need to explore all possibilities with an open mind derives from the secrecy of Sigma Technology . The use of Canon available information about the bus has been to provide basis for possible similarities that can be exploited for analysis.

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