We are running a survey to help us improve the experience for all of our members. If you see the survey appear, please take the time to tell us about your experience if you can.
I'm not having much success in finding an 8031 POST (power on self test) online. I'd be especially interested in tests from a microprocessor manufacturer. For example, are there published tests to verify that the 128 bytes of indirect memory are reliable? Are there simple tests for the SFRs? Thanks for your comments. Robert Berkey
To: Graham Cole I converted your code to 8031 and Keil. The 8031 only has 128 bytes of indirect RAM and lacks some of the registers used in your processor. I also had to substitute for the local labels. I do wish that Keil would add local labels to their assembler. The Keil simulator indicates that this test runs in 80 milliseconds and uses 123 bytes of code space. Our watchdog waits 1.5 seconds before it gets alarmed, so I've removed that feature.
; ; Destructive 8031 Indirect-RAM Test ; Public Domain 2002 ; ; Tests 080H bytes Using Borer Test ; sub_cycles EQU TH0 ; reuse timer 0 register sub_cycle_counter EQU TL0 ; reuse timer 0 register test_pattern EQU B ; register pass EQU F0 ; bit, set=read clear=write test_failed EQU PSW.1 ; bit BSEG SELF_TEST_ALARM: DBIT 1 CSEG ; DESTRUCTIVE_IDATA_TEST: ; CLR TR0 ; assumes timer 0 is stopped ;BEGIN CLR test_failed ; test_failed := false. ; MOV DPTR,#dit_pattern_table ; _1: ; FOR table_pointer := 0 TO 10 D0 SETB pass ; _2: ; FOR pass := write TO read DO ; CLR A ; MOVC A,@A+DPTR ; MOV test_pattern,A ; Read test_pattern. MOV A,#01 ; MOVC A,@A+DPTR ; MOV sub_cycles,A ; Read sub_cycles. ; MOV SP,#00H ; Zero the memory pointer. ; _3: ; FOR memory_pointer := 0 TO 07FH DO ; MOV sub_cycle_counter,sub_cycles _4: ; FOR sub_cycle_counter := sub_cycles TO 1 DO JNB pass,_5 ; IF pass = write THEN ; DEC SP ; PUSH test_pattern ; Write test_pattern to memory. SJMP _8 ; _5: ; ELSE POP Acc ; Read memory. INC SP ; CJNE A,test_pattern,_6 ; IF test_pattern = @memory_pointer THEN SJMP _7 ; OK _6: ; ELSE SETB test_failed ; Test failed. _7: ; ENDIF _8: ; ENDIF INC SP ; Increment memory_pointer. ; DJNZ sub_cycle_counter,_4 ; ENDFOR XRL test_pattern,#11111111B ; Invert the test pattern. MOV A,SP ; CJNE A,#080H,_3 ; ENDFOR JBC pass,_2 ; ENDFOR INC DPTR ; INC DPTR ; Increment the table pointer. MOV A,DPL ; CJNE A,#LOW( dit_pattern_table_end ),_1 MOV A,DPH ; CJNE A,#HIGH( dit_pattern_table_end ),_1 ; ENDFOR MOV C,test_failed ; MOV self_test_alarm,C ; self_test_alarm := result of test. ; DIT_RETURN: LJMP RESTORE_IDATA ;END RESTORE_IDATA: JMP $ ; dit_pattern_table: ; DB 10101010B,1 ;00 DB 01010101B,1 ;00 DB 11001100B,1 ;01 DB 00110011B,1 ;01 DB 11110000B,1 ;02 DB 00001111B,1 ;02 DB 11111111B,1 ;03 DB 00000000B,1 ;03 DB 11111111B,2 ;04 DB 00000000B,2 ;04 DB 11111111B,4 ;05 DB 00000000B,4 ;05 DB 11111111B,8 ;06 DB 00000000B,8 ;06 DB 11111111B,16 ;07 DB 00000000B,16 ;07 DB 11111111B,32 ;08 DB 00000000B,32 ;08 DB 11111111B,64 ;09 DB 00000000B,64 ;09 DB 11111111B,128 ;10 DB 00000000B,128 ;10 ; DB 11111111B,LOW(256) ;11 for newer processors with 256 ; bytes of indirect ram ; DB 00000000B,LOW(256) ;11 dit_pattern_table_end EQU $ ; ; END The destructive RAM test tests all 128 bytes of the internal RAM - using only registers to control the loops and save the results. Note that the Stack Pointer is used to address memory - this is the only way to avoid using R0/R1. The test makes a through check of individual memory cells, detects all but the most exotic addressing faults and will detect most instances where the state of a bit is affected by the state of nearby bits. Note that this routine necessarily trashes the stack. The software invoking the destructive RAM test has to jump to this routine and provide a label to jump back to. The invoking software must then set up the stack etc. Reference: Borer, A.J.: Total Memory Test, Microprocessors and Microsystems, May 1980. Also of interest is: McEliece, R.J.: The Reliability of Computer Memories, Scientific American, January 1985.