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[Previous] [Up] [Top] [Contents] [Back]Chapter 3 Functional Description
The VMEbus interface is used by to access resources on the CC121 module. These resources include a 2-kbyte dual-port data buffer, the ARCNET protocol controller, and some general control registers. The data buffer is used to hold data packets temporarily prior to transmission on the network and as a temporary storage of all received data packets directed to this particular node. The processor writes commands to the protocol controller and can read its status. The onboard control registers are used to read the ARCNET node ID, and to control the interrupt function of the board.
The CC121 occupies 4-kbytes in the VMEbus standard, or short I/O address space. The address selection is made with hexadecimal switches, and the address modifiers are selected with jumpers. The interrupt level is also selected with jumpers, and the interrupt vector is software programmable.
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