Arcnet header




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ARCNET HEADER

Here is a brief description of what we decided to go along with for the ARCNET header. The NODE_ID filed is still the node id on each board. (If possible we will place them in a certain order). The FEMS software uses the reserved nodes (0xF0- 0xFF). The COMMAND field only has a few basic calls such as read and write. The DEVICE TYPE field will select the device being written or read to, such as a serial port, memory address or a data port. The data length is set by the control node and will be modified by the FEM when a read back is requested. If the ERROR fi



eld has a value other than zero, then an error or a reset has occurred at the FEM.


COMMAND WORD FIG 1.


FIELD

BITS

FUNCTION

NODE_ID

31..24

FEM specific field used to select a node at the front end.

DATA LENGTH



15..0

Specifies the total number of bytes in hopper command, including command word and data,

COMMAND WORD TABLE 1.




  • The control node has to have a NODE_ID = 0x01.

  • The NODE_ ID's = 0xF0 -- 0xFF are reserved.

  • The COMMAND field must be placed at the beginning of the hopper memory.

  • The GROUP COMMAND = 0x01 is reserved for a broadcast.

  • The GROUP COMMAND = 0x00 is reserved for a single node transfer.

  • The ERROR field must be set to 0x00 when the control node transmits data.

  • The ERROR filed will return a value other than zero when an error occurs at a FEM. (data length = 0).

  • The ERROR filed will be set to 0x01 when a node is reset for example NODE_ID = 5 & ERROR = 1 node 5 was reset.

  • The control node must be able to receive an ERROR PACKET from any FEM at any given point in time.


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