Subversion Repositories eco32

;

; rom06.s -- "crossed" echo with two terminals, polled

;

        .set    tba0,0xF0300000 ; terminal base address 0

        .set    tba1,0xF0301000 ; terminal base address 1

        add     $8,$0,tba0       ; set $8 to terminal base address 0

        add     $9,$0,tba1       ; set $9 to terminal base address 1

L1:

        ldw     $10,$8,0 ; load receiver status into $10

        and     $10,$10,1       ; check receiver ready

        beq     $10,$0,L3        ; not ready - check other terminal

        ldw     $11,$8,4        ; load receiver data into $11

L2:

        ldw     $10,$9,8        ; load transmitter status into $10

        and     $10,$10,1       ; check transmitter ready

        beq     $10,$0,L2        ; loop while not ready

        stw     $11,$9,12       ; load char into transmitter data

L3:

        ldw     $10,$9,0 ; load receiver status into $10

        and     $10,$10,1       ; check receiver ready

        beq     $10,$0,L1        ; not ready - check other terminal

        ldw     $11,$9,4        ; load receiver data into $11

L4:

        ldw     $10,$8,8        ; load transmitter status into $10

        and     $10,$10,1       ; check transmitter ready

        beq     $10,$0,L4        ; loop while not ready

        stw     $11,$8,12       ; load char into transmitter data

        j       L1              ; all over again