CoCoIO Buffer math outline

No matter what you do with CoCoIO, you'll be managing buffer addresses, based on a few hints from the WizNet chip. This includes starting and ending addresses and possible wraparound mid segment. Don't forget to reset the next read location when you are done! 

The overall process:

  • Use IRQ or periodically poll the Received Size Register. If >0 ...
  • Get the read or write pointer, AND to the buffer mask (buff size -1)
  • Add to the buffer base address. This is the start location.
  • Get the rx/tx data size.
  • Subtract from end of buffer. This is sizeof first segment.
  • Read that many bytes from the dataport.
  • Reset the rx/tx pointer to the start of the buffer.
  • Read the remaining bytes from the dataport.
  • Set the read pointer one address past the last one read
  • Send RECV ($40) to the socket command register

If you'd rather think in code, here is a Basic09 procedure to do the above. It's assuming we will always use socket one (everywhere $FF69,$04 appears could also be $05,$06,or $07).

PROCEDURE bufmath (* bare outline of buffer math 8/19/21 ricku (* DIM raddr,rbase,rend,rmask,roff,rsize,rptr,rmax,segment:INTEGER DIM int1,int2,int3,int4:INTEGER (* rbase - base address of read buffer (* rmask - buffer size mask (* rptr - raw ptr from Wizzy. AND with mask to get roff (* roff - read offset from start of buffer (* rend - end of read buffer (* raddr - absolute read address (* rsize - total bytes to injest (* segment - bytes to injest (to EOB or after wraparound) (* At this point you have sent a request to the server (* and are waiting for data (* ____________________________________________ start of read page LOOP (* FIXME _____ POLLS say IRQs are better! REPEAT POKE $FF69,$04 \ POKE $FF6A,$26 \ (* get Sn_RX_RSR recv size rsize:=PEEK($FF6B)*256+PEEK($FF6B) UNTIL rsize<>0 segment:=rsize \ rbase:=$6000 POKE $FF69,$04 \ POKE $FF6A,$1E \ (* Sn_RXBUF_SIZE int1:=PEEK($FF6B)*256+PEEK($FF6B) rmask:=1024*int1-1 POKE $FF69,$04 \ POKE $FF6A,$26 \ (* Sn_RX_RSR rsize:=PEEK($FF6B)*256+PEEK($FF6B) POKE $FF69,$04 \ POKE $FF6A,$28 \ (* Sn_RX_RD rptr:=PEEK($FF6B)*256+PEEK($FF6B) int1:=INT(rptr/256) \ int2:=rptr-256*int1 int3:=INT(rmask/256) \ int4:=rmask-256*int3 int1:=LAND(int1,int3) \ int2:=LAND(int2,int4) roff:=int1*256+int2+rbase (* _____________________________________________ parse the frame raddr:=rbase+roff IF roff+rsize>rend THEN segment:=rmask+1-roff (* GOSUB - process segment bytes of data raddr:=rbase \ segment:=rsize-rend (* GOSUB - process segment bytes of data ELSE segment:=rsize (* GOSUB - process segment bytes of data ENDIF (* __________________ end of a frame. increase Sn_RX_RD by rsize POKE $FF69,$04 \ POKE $FF6A,$28 rptr:=PEEK($FF6B)*256+PEEK($FF6B)+rsize POKE $FF69,$04 \ POKE $FF6A,$28 int1:=INT(rptr/256) \ int2:=rptr-256*int1 POKE $FF6B,int1 \ POKE $FF6B,int2 POKE $FF69,$04 \ POKE $FF6A,$01 \ POKE $FF6B,$40 \ (*Sn_CR to RECV ENDLOOP