[-dMk!-]

и ещё процитирую сообщение Павла Соколова с dpreview:

Forum Sigma SLR Talk
Subject I found this information about canon/sigma signal system
Posted by Pavel Sokolov [CLICK FOR PROFILE]
Date/Time 11:32:08 PM, Sunday, January 30, 2005 (GMT)

Pinout and pin functions:

Left to right, looking at the front of the body:

1. VBAT
2. P-GND
3. P-GND (pins 2 & 3 are common on the lens)
4. VDD
5. DCL
6. DLC
7. LCLK
8. D_GND

Pin Functions
VBAT - Motor power
P_GND - Motor power ground
VDD - Logic circuitry power
D_GND - Logic circuitry ground
DCL - Data from body to lens
DLC - Data from lens to body
LCLK - Clock

Data protocol: Motorola SPI; 8 bit serial; Such as the protocol used with the 68HC05 chip.