Post by thread:Binary to BCD was: separating digits (decimal disp

Stewart Pye wrote: > > Thanks for the help, but it's not exactly what I was looking for. I need to > display it as a decimal number. I've done it on an 8051 but the pic doesn't > have divide. There's got to be some way to do it but it eludes me. Oh, I didn't read your original post (closely). Here's something I posted a while back that should do the trick. But I'm sure others will soon tell you that there are other techniques too. In fact, Reggie just posted something less than a week ago that does the same thing for 16 bit numbers. Mike Keitz has a cute little looping trick that is optimized version of what you'll find in Microchip's appnotes. If you subscribe to the Pic list long enough, you'll see these routines posted every three months or so. Maybe we should put all of the 'answers' to all pic questions on a web and then the piclist can be become 100% [OT] instead of 90% :). =============================================================== Ancient post: Here's the 28-cycle (non-looping) version that I promised yesterday. It's based on binary comparisons. It's one of those routines that is very difficult to comment. So I didn't. However it takes advantage of this little trick to quickly ascertain the ones' digit: If you look at the ones' digit for 2^N you see this pattern: n = 0, 1, 2, 3, 4, 5, 6, 7, 8, 9,10,11 ... 2^n % 10 = 1, 2, 4, 8, 6, 2, 4, 8, 6, 2, 4, 8 ... If it wasn't for the annoying 6's, you could simply sum the nibbles to get and get the ones' digit (after a relatively simple binary to BCD conversion). However, it's simple enough to test if bit 4, 8,... are high and to subtract 1 and then add 6 (or simply add 5) if they are. The second observation is that the sum of all of the tens' digits is less than 16, and thus can fit into one nibble. This simplifies having to deal with overflow until after all of the digits have been added together. The third observation is that the BCD result is greater than 200 only if the most significant bit is set. ;******************************** ;binary_to_bcd - 8-bits ; ;Input ; bin - 8-bit binary number ;Outputs ; hundreds - the hundreds digit of the BCD conversion ; tens_and_ones - the tens and ones digits of the BCD conversion binary_to_bcd: CLRF hundreds SWAPF bin,W ADDWF bin,W ANDLW 00001111b SKPNDC ADDLW 0x16 SKPNDC ADDLW 0x06 ADDLW 0x06 SKPDC ADDLW -0x06 BTFSC bin,4 ADDLW 0x16 - 1 + 0x6 SKPDC ADDLW -0x06 BTFSC bin,5 ADDLW 0x30 BTFSC bin,6 ADDLW 0x60 BTFSC bin,7 ADDLW 0x20 ADDLW 0x60 RLF hundreds,F BTFSS hundreds,0 ADDLW -0x60 MOVWF tens_and_ones BTFSC bin,7 INCF hundreds,F Scott