I'll have to try that code. Here is some sample data from a 1630 IA file that I was looking at last time:
The first two bytes 0x00FA is the block length, and I assume those bytes would not be included in the checksum. I believe the next four bytes 0x00003050 is the load address of the data block, and probably included in the checksum, but maybe not. Then I assume the final two bytes 0x0180 is the checksum.
0x00,0xfa,0x30,0x50,0x00,0x00,0xe0,0x00,0x02,0x02,0x00,0x00,0x00,0x00,0x02,0x00
0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x03
0x00,0x00,0xff,0xff,0x00,0x00,0x00,0x03,0x00,0x00,0x00,0x00,0xff,0x00,0x00,0x03
0x00,0x3c,0x00,0x00,0x00,0x00,0x00,0x03,0x00,0x00,0x00,0x00,0x00,0x00,0x20,0x20
0x20,0x20,0x20,0x6d,0x65,0x6d,0x77,0x72,0x6d,0x65,0x6d,0x72,0x64,0x6f,0x70,0x66
0x63,0x68,0x20,0x20,0x20,0x20,0x20,0x20,0x20,0x20,0x20,0x20,0x20,0x20,0x20,0x20
0x20,0x20,0x20,0x20,0x20,0x20,0x20,0x20,0x20,0x20,0x20,0x69,0x6f,0x20,0x77,0x72
0x69,0x6f,0x20,0x72,0x64,0x69,0x6e,0x74,0x61,0x6b,0x20,0x20,0x20,0x20,0x20,0x20
0x20,0x20,0x20,0x20,0x20,0x20,0x20,0x20,0x20,0x20,0x20,0x20,0x20,0x20,0x20,0x20
0x20,0x20,0x20,0x20,0x20,0x20,0x20,0x20,0x20,0x20,0x20,0x20,0x20,0x20,0x20,0x20
0x20,0x20,0x20,0x20,0x20,0x20,0x20,0x20,0x20,0x20,0x20,0x20,0x20,0x20,0x20,0x20
0x20,0x20,0x20,0x20,0x20,0x20,0x20,0x20,0x20,0x20,0x20,0x20,0x20,0x20,0x20,0x20
0x20,0x20,0x20,0x20,0x20,0x20,0x20,0x20,0x20,0x20,0x20,0x20,0x20,0x20,0x20,0x20
0x20,0x20,0x20,0x20,0x20,0x20,0x20,0x20,0x20,0x20,0x20,0x20,0x20,0x20,0x02,0x02
0x00,0x00,0x00,0x00,0x02,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00
0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x03,0x00,0x00,0x00,0x00
0x01,0x80