The Microcontroller Idea Book - Jan Axelson's Lakeview Research

Jumper J4 is optional. It enables you to write-protect U8 by jumpering WE to +5V. You might
want to do this if you have critical programs or data stored in U8, and you want to be sure
that you don’t overwrite them accidentally.
Wiring Tips
When you add the circuits for NV memory, use sockets for U8 and U9. If you previously
tied unused pins 9 and 10 of U3 to ground or +5V, be sure to remove these connections
before you wire the ones shown in Figure 4-3. Since pins 4, 5, 9, 10, 12, and 13 of U9 are
unused CMOS inputs, you should wire these to +5V or ground. You may instead use a
74LS32 for U9. If you do so, leave the unused inputs open.
Using the Programming Commands
When Figure 4-3’s circuit is added, you’re ready to power up and try the programming
commands. Begin by entering any simple BASIC-52 program, such as one of the examples
in Chapter 3.
Setting MTOP
If you have a 32K RAM at U7, you have an additional step to perform before you store a
program in U8. On bootup, BASIC-52 tests contiguous memory and sets MTOP to the
highest value it finds below E000h. But BASIC-52’s programming commands won’t work
unless MTOP is below 8000h. To enable program storage, type the following command:
MTOP=7FFFh
This ensures that BASIC-52 won’t try to store RAM programs, variables, or strings in the
area that you’ve reserved for permanent program storage (although it doesn’t prevent you
from writing to the area with BASIC-52’s XBY operator). If U7 is an 8K device, MTOP is
1FFFh, well below 8000h, so you don’t have to worry about changing it.
Saving a Program
To copy the current program from U7 to U8, type
FPROG
Saving Programs
The screen will display the number 1, indicating that this is the first BASIC-52 program to
be stored in the device, and after a short delay, the READY prompt should return.
PROG is an alternate command that uses a slower programming algorithm, and should also
work.
The Microcontroller Idea Book 53