The Microcontroller Idea Book - Jan Axelson's Lakeview Research

Programming
• Hexadecimal numbers that begin with A through F must have a leading 0, and all
hexadecimal numbers must end in H. Here are some examples of valid hexadecimal
numbers:
Valid Hex Number
Decimal Equivalent
0DH 208
0AH 10
15H 21
0FFFFH 65,535
0CH 12
Here are some invalid hex numbers, and a valid hex number that doesn’t have its intended
value:
Invalid Hex Number
Problem
FFH no leading 0
0C
no trailing H
10 (intended as decimal 16) no trailing H. BASIC-52 will interpret at
decimal 10 (0AH)
BASIC-52 Bugs and Things to Watch Out For
This section is a summary of other bugs and other minor problems with BASIC-52 to be
aware of as you program. Many of BASIC-52’s bugs and limits have been eliminated in
newer versions of BASIC-52 developed by other sources, described in Chapter 15.
Assembly-language Issues:
In external code memory, if 2002h contains 5Ah and bit 5 at 2048h is set, BASIC-52 will
try to call a user-written token table. If 2001h contains 0AAh, BASIC-52 will try to call a
user-written reset routine at 2090h. If the expected table or routine isn’t present, the system
will crash. (See Chapter 13.) Solution: avoid writing to code memory at 2001h, 2002h, and
2048h. (In Figure 3-1’s circuit, the RAM in this area (if any) is accessed as data memory
only, so you don’t have to worry about this.)
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