Many thanks, Ingo! Greatly appreciate your support.
Adding PSEN and ALE (as analog signals) helped to identify beyond doubt the start up of uC.
I still get differing captures but the differences seem to be 'interjections' of FF and some other hex numbers. Or is this just wishful thinking?
Have a look please at two different captures and the respective decoded beginnings.
At the beginning of the 2nd full cycle of ALE/33.2 us I get the 8B at adress 0002
The mouse pointer is at 8B
==========================================
Different capture:
How does this look with regards to the uC starting the commands in the EEPROM?
These are the corresponding HEX numbers inside the EEPROM
00 01 02 03 04 05 06 07 08 09 0A 0B 0C 0D 0E 0F
00000000 02 02 8B C2 8B 41 2D FF FF FF FF D2 90 C2 0A 32 ..?Â?A-....Ò?Â.2
00000010 FF FF FF 05 36 30 1C 44 32 FF FF D5 2A 13 11 22 ....60.D2..Õ*.."
00000020 41 8B 32 10 99 08 A8 99 C2 9B 86 99 C2 98 C2 89 A?2.?.¨?Â???Â?Â?
00000030 32 10 94 0E D2 94 85 43 8D 85 42 8B 20 1C 02 C2 2.?.Ò??C??B? ..Â
00000040 89 32 85 47 8D 85 46 8B 85 45 43 85 44 42 85 36 ?2?G??F??EC?DB?6
00000050 37 75 36 00 D2 17 20 1C 02 C2 89 32 D5 2B 31 D5 7u6.Ò. ..Â?2Õ+1Õ
00000060 2D 03 12 10 00 53 A8 EA 11 AA 30 8B FD 05 36 C2 -....S¨ê.ª0?ý.6Â
00000070 8B D5 2D 03 12 10 00 20 10 0D 20 B3 03 30 8B FA ?Õ-.... .. ³.0?ú
00000080 B2 91 20 8B 07 01 82 30 8B FD B2 91 D2 AA 01 AB ²? ?..?0?ý²?Òª.«
00000090 D5 2D 17 12 10 00 53 A8 EE 11 AA C0 E0 C0 D0 C0 Õ-....S¨î.ªÀàÀÐÀ
000000A0 83 C0 82 C0 F0 90 21 A0 21 58 32 C0 E0 C0 D0 C0 ?À?Àð?!*!X2ÀàÀÐÀ
000000B0 83 C0 82 C0 F0 90 21 A0 20 91 13 E4 A2 10 35 30 ?À?Àð?!* ?.ä¢.50
000000C0 13 14 92 10 C2 AA 25 2B F5 2B D2 AA 21 58 E4 A2 ..?.ª%+õ+Òª!Xä¢
000000D0 10 35 33 95 31 C3 95 59 C3 95 2F 40 05 B4 12 00 .53?1Ã?YÃ?/@.´..
000000E0 50 0A C3 94 12 25 59 F5 59 74 12 C3 13 14 92 10 P.Ã?.%YõYt.Ã..?.
000000F0 C2 AA 25 2B F5 2B D2 AA 74 03 25 35 93 C2 AA 25 ª%+õ+Òªt.%5?ª%
00000100 2D F5 2D D2 AA 51 5A C2 89 D2 A8 75 D0 18 02 10 -õ-ÒªQZÂ?Ò¨uÐ...
00000110 29 D5 34 44 75 F0 2C 20 16 0F 75 F0 2A 20 15 09 )Õ4Duð, ..uð* ..
00000120 75 F0 28 20 14 03 75 F0 26 E5 F0 93 F5 34 05 F0 uð( ..uð&åð?õ4.ð
00000130 E5 F0 93 F5 F0 E5 32 C3 95 31 C3 30 E7 0E F4 04 åð?õðå2Ã?1Ã0ç.ô.
00000140 95 F0 E5 32 40 10 E5 31 95 F0 21 56 95 F0 E5 32 ?ðå2@.å1?ð!V?ðå2
00000150 40 04 E5 31 25 F0 F5 31 C2 89 D2 A8 10 37 02 41 @.å1%ðõ1Â?Ò¨.7.A
00000160 22 75 D0 18 74 01 93 05 35 B5 35 0F 75 35 00 90 "uÐ.t.?.5µ5.u5.?
00000170 00 00 F0 F0 F0 F0 90 21 A0 21 A3 20 1A 25 10 0F ..ðððð?!*!£ .%..
00000180 02 41 22 75 F0 40 E5 4E A4 FE AF F0 30 0A 02 80 .A"uð@åN¤þ¯ð0..?
00000190 03 02 01 F8 C2 8C C3 E5 8A 9E F5 8A E5 8C 9F F5 ...øÂ?Ãå??õ?å??õ
000001A0 8C 41 0D C3 74 11 93 95 37 72 1D 40 6E AE 4C AF ?A.Ãt.??7r.@n®L¯
000001B0 4D 02 10 2C 20 1A 41 30 0D 2D E5 4F B4 10 00 40 M.., .A0.-åO´..@
000001C0 0C C2 0D 30 16 05 C2 16 75 34 01 21 E7 90 21 80 .Â.0..Â.u4.!ç?!?
@Gilles: the 27C256 has the same contents as a 27C128 in both its upper and lower half of the adresses, just like Ingo wrote.