Resetting

For a proper reset the following steps have to be taken:

1. load the appropriate value in FIFO_INIT (to select P, see below)
2. write to RESET: all registers are set to zero except the FIFO_INIT register value which is loaded into the FIFO's Programmable Flag Register (PFR)

[1]see Resetting subsection

The status of the contents of the FIFO is indicated by a set of 3 flags (HF, E/F and PAFE (Programmable Almost Full/Empty Flag), all 'low active') which can be read from the AST's statusregister.

The status of the flags is an indication of the number of words in the FIFO, as shown in table 3. The constant P is programmable and depends on the value written in the FIFO_INIT register; table 4 gives an overview of the available options for P.

 
Table 3: AST FIFO flags. 

 
Table 4: Data to write into the FIFO_INIT register to select a value for P.