Converting a 16-bit number into decimal format. Assume the low 8-bits in X and the high 8-bits in Y. Also assume at the beginning of the pattern table (whichever one is going to be used for displaying these numbers) has numbers 0 to 9 repeated a few times. You will have tables DL0, DL1, DH0, etc for converting one digit into the decimal (each table is 256 bytes long).
CLC LDA DL0,X ADC DH0,Y STA <DIGIT0 CMP #10 LDA DL1,X ADC DH1,Y STA <DIGIT1 CMP #10 LDA DL2,X ADC DH2,Y STA <DIGIT2 CMP #10 LDA #0 ADC DH3,Y STA <DIGIT3 CMP #10 LDA #0 ADC DH4,Y STA <DIGIT4
If the numbers are not at the beginning of the pattern table, you can alter the tables for converting the high 8-bits into decimal, and change #10 into the different number by the bias of the carry that is used in this case.