Radio Shack TRS-80 Model II Reference Manual page 95

CHARACTER
NUMBER
CONTENTS
Library Commands
COMMENTS
10
+
(N*2) First byte of data
checksum (high
nibble)
11
+
(N*2) Second byte of
data checksum
(low nibble)
Sample record:
ThiS pair represents 2's cQmplementqf
the data (all byte pairs afterthe.":"uptq
but not including the checksum). Note that
each byte pair is converted back.tothe
original byte of data before it is summed.
CHARACTER
NUMBER
SAMPLE DATA
ASCII HEX VALUE
2
3
4
5
6
7
8
9
10
11
12
13
14
15
"0"
"7"
"A"
"3"
3A
30
32
32
38
30
30
30
30
33
37
37
30
41
33
This record will contain 2 byte-pairs of data:
"3" "7"
representing the value X'37'
"7" "0" representing the value X'70'
and will start loading at X'2800'. The one-byte sum of the original bytes (represented
in pairs by characters 2 through 13) is X'5D'. The 2's complement ofX'5D' is X'A3'
- which is represented in bytes 14 and 15.
131