[1st edition Digital8] Q&A-04: How to calculate CHEKSUM ? Date: Sat, 07 Oct 2000 18:19:15 +0200 From: Rainer.vom.Dorp@t-online.de (Rainer vom Dorp) To: "Mijo K." Hi, I tried to analyse the calculation of the checksum, because every single enabled function worked. For nearly all sony cams 'even parity' checksum is used. Here it is how it workes (see "other functions for TR7000E..." on site http://lea.hamradio.si/~s51kq/DV-IN.HTM 1) let's assume enabling DV-In and recording is allready done => we don't have to consider adr. 0x14, 0x15, 0x27 on page 0x0d. 2) the left adr. on page 0x0d are 0x17, 0x18, 0x1e, 0x20, 0x24, 0x25, 0x26 and checksum at adr. 0x23. 3) we have to calculate the difference between the original and the modified data: adr. 0x17 old 0x77 = 0111 0111 cam.mode -> seen, when "EXPOSURE" new 0xf7 = 1111 0111 button is pressed xor = 1000 0000 adr. 0x18 old 0x40 = 0100 0000 cam.code -> "VF-SET" -> "ZEBRA" new 0x60 = 0110 0000 xor = 0010 0000 adr. 0x1e old 0x88 = 1000 1000 (green area for TRV7000E) new 0x8a = 1000 1010 cam.mode -> new menue entry: xor = 0000 0010 "MANUAL SET" -> "WHT.BAL" adr. 0x20 old 0x0b = 0000 1011 (green area for TRV7000E) new 0x1b = 0001 1011 cam-mode -> "SETUP MENUE" -> xor = 0001 0000 "AUTO-TV ON" + "TV INPUT" adr. 0x24 old 0x01 = 0000 0001 cam.mode -> "CAMERA SET" -> new 0x19 = 0001 1001 "FRAME REC" + "INT.REC" xor = 0001 1000 adr. 0x25 old 0x00 = 0000 0000 cam.mode -> "OTHERS" -> "COLOUR BAR" new 0x81 = 1000 0001 xor = 1000 0001 adr. 0x26 old 0x00 = 0000 0000 play.mode -> "OTHERS" -> "DV EDITING" new 0x10 = 0001 0000 xor = 0001 0000 4) calculate even parity for checksum byte at adr. 0x23: adr. 0x17 xor = 1000 0000 adr. 0x18 xor = 0010 0000 adr. 0x1e xor = 0000 0010 adr. 0x20 xor = 0001 0000 adr. 0x24 xor = 0001 1000 adr. 0x25 xor = 1000 0001 adr. 0x26 xor = 0001 0000 ----------- even parity = 0011 1011 = 0x3b 5) as you see, it's not 0x38 but 0x3b ! 6) I used this value and it worked, even when battery and powersupply are removed for some minutes. Very fascinating during my nightly examinations was: every change could be seen at once at the cams menue (see above). So, what is left now ? I've learned a lot and I will try to enable these functions on my friends TRV320 next week (if there is time for that). The main problem is: at what location are the checksums ? If you have an idea, please let me know, as I will do so either. happy enabling Rainer