{{ :huce:microlab:projects:internal:gecko:gecko3:system_bus:gecko3main_front.png?200|}}

====== GECKO3 system bus =======

The GECKO3 project defines a 240-pin system bus. Only about one quarter of these pins is assigned to fixed functions, however one must ensure compatibility between two modules, which could accidentally use the same pins for different signals.

//IO1// is the main connector and delivers power and signals to the system's modules. 
It is situated directly beneath the board's edge. //IO2// is only used for GPIOs.

{{:huce:microlab:projects:internal:gecko:gecko3:system_bus:tyco-free-height-8mm-blend.jpg?200 |}}Both connectors are Tyco Electronics [[http://catalog.tycoelectronics.com/TE/bin/TE.Connect?C=1&M=BYPN&PN=5179030-5&I=13|Free Height]] (FH) connectors with 0.8 mm pin spacing. 
([[http://www.te.com/commerce/DocumentDelivery/DDEController?Action=showdoc&DocId=Specification+Or+Standard%7F108-5390%7FE%7Fpdf%7FEnglish%7FENG_SS_108-5390_E.pdf%7F5179030-5|Tyco FH 0.8mm Datasheet]]). These series of connectors allows board-to-board distances from 5 to 13 mm.

{{:standards:tyco-free-height-8mm-blend.jpg?300&nolink|Tyco Free Height (FH) male and female, 8 mm board to board distance}}

The system bus is logically subdivided into parts of 8 bits. So each part represents one byte. There are 9 bytes on the IO1 and 14.5 bytes on the IO2 available.

==== Bus pin discriptions ====
    * The system bus ordered by the pin header numbers is available on System bus in [[mechanical_order|mechanical order page.]] 
    * The system bus ordered by the logical blocks is available on System bus in [[logical_order|logical order page.]]