Read-Modify-Write FASTBUS Instructions

The following opcodes may be used to construct Read-Modify-Write FASTBUS operations. AS remains up until the next primary address or normal non-FASTBUS instruction.

Code  Mnemonic  Type  Description 
20    LAF       RX    Load address, AS up 
21    BCTF      RX    Branch on Count, AS up 
22    BCF       RX    Branch conditional, AS up 
23    STF       RX    Store, AS up 
24    NF        RX    And, AS up 
25    OF        RX    OR, AS up 
26    XF        RX    X-OR, AS up 
27    LF        RX    Load, AS up 
28    CF        RX    Compare, AS up 
29    AF        RX    Add, AS up 
2A    SF        RX    Subtract, AS up

The following instructions may be used to construct a FASTBUS instruction to ignore SS codes at Primary or Secondary address and perform a subsequent data cycle

  30   FPAI      RS   Primary address, ignore SS codes 
  31   FPWNTAI   RS   Secondary address, ignore SS codes 
  32   FPWIG     RS    FASTBUS write, ignore SS code

** FPWNTAI does not work correctly **