5.3 CC121 Memory Map

The local memory map takes a total of 4 kbytes in the VMEbus standard or short address space. It has been divided in two 2-kbyte segments, where the first part is used to access the dual-port data buffer, and the second part the 8-bit devices.

The total memory map is shown in the next table. Note that address spaces marked with (*), are repeated a number of times in the memory map. The number of times depends on the space that the peripheral occupies in the memory map. The size indication shows the allowed data transfer width. Note that only the 2-kbyte data buffer can be accessed for 16-bit transfers. The other peripherals must be accessed for 8-bit transfers and addressed at odd memory locations.

CC121 Memory Map
Address	Device	Size
xxx000 xxx7FF	Dual-port Data Buffer 2Kbyte	8, 16 bit
xxx800 xxx9FF	COM9026 (*) 2 bytes	8 bit
xxxA00 xxxBFF	Interrupt Vector Register (*) 1 byte	8 bit
xxxC00 xxxDFF	Board Control Register (*) 1 byte	8 bit
xxxE00 xxxFFF	Node ID Switch Register (*) 1 byte	8 bit

The next sections describe the devices in the memory map in more detail.

5.3.1 - Dual-port Data Buffer
5.3.2 - COM9026 ARCNET Interface
5.3.3 - Interrupt Vector Register
5.3.4 - Board Control Registers
5.3.5 - Node ID Switch

CC121 - ARCNET Interface for VMEbus - 30 SEP 1996

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