; File name: sattest.asm
;
; C5402 demonstration test code
;
; 31Jan02 .. initial version .. KM

      .mmregs

         .data

         .bss onefourth,1
      
         .text
            
         .global _c_int00    
                    
_c_int00:
        
         ; test the effects of the sign extension bit
        
         ssbx     sxm            ; turn sign extension on
         ld       #0,a           ; zero the a accumulator
         ld       #0,b           ; zero the b accumulator
         ld       #0FFFFh,b      
         nop
         nop
        
         rsbx     sxm            ; turn sign extension off
         nop
         ld       #0FFFFh,a
         ld       #0,b  
         nop
         nop          
        
         ; investigate sst bit effect + overflow
                
         ssbx     sxm            ; turn sign extension on   
         ld       #0,a           ; zero the a accumulator   
         ld       #0,b           ; zero the b accumulator
         add      #07000h,16,a   ; add 7/8 in fractional format
         add      #07000h,16,a   ; sum is 1 5/8   
         andm     #0FFFEh,pmst   ; set SST to no saturation   
         nop                     ; had pipeline warning
         nop                     ; had pipeline warning     
         nop                     ; had pipeline warning
         sth      a,*(bh)
         nop
         nop
         nop                   
         orm      #00001h, pmst  ; set sst to saturate
         ld       #0,b           ; zero the b accumulator  
         nop                     ; had pipeline warning 
         nop                     ; had pipeline warning
         sth      a,*(bh)    
         nop
         nop
         nop   
        
            ; investigate sst bit effect - overflow
        
         ssbx     sxm            ; turn sign extension on   
         ld       #0,a           ; zero the a accumulator   
         ld       #0,b           ; zero the b accumulator
         add      #09000h,16,a   ; add -7/8 in fractional format
         add      #09000h,16,a   ; sum is -1 5/8   
         andm     #0FFFEh,pmst   ; set SST to no saturation   
         nop                     ; had pipeline warning
         nop                     ; had pipeline warning     
         nop                     ; had pipeline warning
         sth      a,*(bh)        ; stores positive value not negative
         nop
         nop
         nop                   
         orm      #00001h, pmst  ; set sst to saturate
         ld       #0,b           ; zero the b accumulator  
         nop                     ; had pipeline warning 
         nop                     ; had pipeline warning
         sth      a,*(bh)        ; interesting..did not sign extend
         nop                     ; would have been ok if there were
         nop                     ; not an accumulator...look out!
         nop          
        
here:    b  here