+-------+
                                XCSR:   |   0   |
                                        +-------+
 
                                +--------+
                        OTTPS:  | XCSR   |
                                +--------+
                        PTTPS:  |c(XCSR) |
        +-------+               +--------+
$TTPS:  |       |-----> TTPS:   |c(XCSR) |
        +-------+               +--------+
 
                                +--------+
                        OTTPB:  | XDAT   |
        +-------+               +--------+
$TTPB:  |       |-----> TTPB:   |        |
        +-------+               +--------+
 
                                +--------+
                        OXTTPS: | TPSRTN |
        +-------+               +--------+
$XTTPS: |       |-----> XTTPS:  Simulated XCSR action routine
        +-------+
 
                                +--------+
                        OXTTPB: | TPBRTN |
        +-------+               +--------+
$XTTPB: |       |-----> XTTPB:  Simulated XDAT action routine
        +-------+