The Microcontroller Idea Book - Jan Axelson's Lakeview Research

2048h in code memory. This is because BASIC-52 checks these locations on bootup to
determine what additions have been made to BASIC-52. If you by chance have certain data
stored at these locations, BASIC-52 will look for the additions it thinks you have, and crash
when it doesn’t find them.
If you have an EPROM addressed at 8000h, and you don’t need the entire EPROM for
BASIC-52 programs, you can store your assembly-language routines in the unused area.
BASIC-52’s (F)PROG command stores programs in sequence beginning at 8010h, so to
leave the most room for BASIC programs, you should place your assembly-language
routines in the EPROM’s highest addresses.
You can also add NVRAM or EPROM in any unused area of combined code/data memory.
For example, you could add an 8K NVRAM addressed from 2000h to 3FFFh, or a 16K
EPROM from 4000h to 7FFFh.
Software for Uploading
You’ll also need a way to load your routines from your personal computer into your
8052-BASIC system’s memory. All that’s required here are your host computer’s communications
software and a BASIC-52 program that reads and stores the uploaded file.
Appendix B contains two such programs. Listing B-1, HEX2RAM.BAS, loads Intel Hex
files from your personal computer into RAM, including NVRAM, in a BASIC-52 system.
Listing B-2, HEXLOAD.BAS, does the same, and also offers the options of loading into
EPROM or EEPROM.
On your host computer, you can the same communications software that you use to upload
BASIC-52 programs, as described in Chapter 3.
Another option for loading routines from your host computer into memory is to program an
EPROM or other device with a device programmer, and then insert the programmed device
into your BASIC-52 system. If you use this method, you can access the chip as code-only
memory, rather than combined code/data memory, since you don’t need to write to it when
it’s installed in the 8052-BASIC system.
Loading a Routine
Calling Assembly-language Routines
When you have the necessary tools, you’re ready to write an assembly-language routine and
assemble, upload, and call, or run, it. As a first try, we’ll begin with a very simple routine,
just to verify that the circuits and techniques are working.
Listing 13-1 has just one function: it toggles pin 1 (Port 1, bit 0) of the 8052. An ORG
directive tells the assembler the address at which to begin loading the routine. Listing 13-1
The Microcontroller Idea Book 221