Loading the FIFO

The FIFO can hold 32 K data items (tokens), each data item having 9 bits; filling the FIFO with data is performed on a token-by-token basis as follows:

1. write the token into register FIFO_DATA
2. write to WRITE_FIFO to load the token into the FIFO

Trying to load the FIFO while the 'run'-bit is on and the AST is in circulate mode (see next subsection) results in a VME bus-error.

Table 5 lists all 256 available control tokens, their use by the HOTLINK chips (parallel-to-serial and serial-to-parallel convertors), and their mapping to VME interrupt numbers of the AORTA-R V2 (in VME it offers 16 different control-token interrupts); only the tokens marked by HOTLINK as being 'free for user' (0 to 4, 6 to 11) can be used freely in the AST/AORTA communication.

 
Table: Control tokens, their use by the HOTLINK chips, and the mapping on AORTA-R V2 interrupt numbers (see [3]).