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Jan Waclawek
11/15/05 10:09
Read: 669 times

#103757 - logic analyser
Responding to: Ravi Shankar Ks's previous message
The LA is basically nothing else just a sequencer which generates successive addresses and a memory where the data are stored. You can try to do a simple loop like:
        MOV  A,P1
        MOVX @DPTR,A
        INC  DPTR
        MOV  A,DPH
        CJNE A,#HIGH(MEM_END),Grab
(of course after proper initialisation of DPTR) and fill up an external memory with 8-bit data attached on port P1. Later you can transfer it to PC and process further. This example reaches a whopping 140ksamples/s on the vanilla 8051 at 12MHz, but on faster '51 clones you could possibly achieve above 2Msamples/s (although you need much more to actually see 0.5us wide pulses - at least 5Msamples or better), especially if you unroll the loop and use features of the faster clones such as autoincremented DPTR (for features of fast clones see e.g. the overview at my homepage). However, for faster sampling rates you will need to implement a separate logic (today often implemented in CPLD or FPGA) which will do the fast address sequencing, and use a fast memory. I am somewhat involved in an amateur LA construction ("miniLA") published at (see also the links given there); and I am also preparing a simpler construction ("pikoLA"), 16 bits at 66 MSamples/s, controlled by - surprise, surprise - '51... (coming in December... hopefully).

Jan Waclawek

List of 12 messages in thread
Digital Pattern Logging (logic analyser)      Ravi Shankar Ks      11/15/05 09:42      
   your pictures      Jan Waclawek      11/15/05 09:50      
   try a f12x the PCA can clock at 100 MHz      Erik Malund      11/15/05 09:50      
      Thanks JW for
 and EM for PCA      
Ravi Shankar Ks      11/15/05 10:05      
   logic analyser      Jan Waclawek      11/15/05 10:09      
      just for fun, I calculated it for a f120      Erik Malund      11/16/05 10:29      
         cost per value      Jan Waclawek      11/16/05 13:43      
            as I said, "just for fun"      Erik Malund      11/16/05 13:55      
         Error, or ...      Slobodan Mandaric      11/17/05 02:36      
            instr.timing on 1clockers      Jan Waclawek      11/17/05 05:31      
            The f12x is a 1 clocker and, as many red      Erik Malund      11/17/05 06:11      
   cypress fx2, DMA, USB 2.0      Frieder Ferlemann      11/17/05 16:31      

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