fuses.mu4

| This file is part of muforth: https://muforth.dev/
|
| Copyright 2002-2024 David Frech. (Read the LICENSE for details.)

loading AVR fuse byte generator

| comment %%
|   You can define any or all of the following values. Leaving any of them
|   undefined will result in the default value from the datasheet for those
|   fuse bits. ckdiv8 is an exception: I'm changing the default to *off*.
|
|   For on/off booleans, fuse bits are 1 if *undefined* (false) and 0 if
|   *defined* (true).
|
|   For fields that define several possibilities, the default binary bit
|   pattern is given.
|
|   Symbol    Default   Comment
|   ~~~~~~    ~~~~~~~   ~~~~~~~
|   eesave    1         don't erase the EEPROM contents when chip is erased;
|                       default value means *do* erase the EEPROM
|   wdton     1         watchdog always on; default means *off*
|   bootrst   1         reset vector is in boot region; default is at 0000
|   bootsz    00        size of boot region; 0 to 3; 0 largest, 3 smallest;
|                       default to *largest*
|   ckdiv8    1         divide clock by 8; default to false (differs from datasheet!)
|   ckout     1         generate a clock on the CLKO pin; default: don't generate
|   cksel     0010      clock select; 0 to 15; default is 8M internal RC
|   sut       10        start up timer (see datasheet)
|   bodlevel  111       brownout detect level; default to no brownout detect
| %%

| Clock settings
| ~~~~~~~~~~~~~~
|
| For a breadboarded chip with no external crystal, resonator, or
| oscillator, use the default clock settings.
|
| For an Arduino or any other setup using an external *crystal* or *ceramic
| resonator*, you have two options. The "official" Arduino fuse settings
| specify the low-power oscillator; however, the full-swing oscillator is
| better in electrically noisy environments. Both use the longest startup
| time (sut = %11).
|
| External crystal/resonator, low-power oscillator:
|       %1111 constant cksel
|         %11 constant sut
|
| External crystal/resonator, full-swing oscillator:
|       %0111 constant cksel
|         %11 constant sut
|
| If using an external *oscillator*, use the following:
|       %0000 constant cksel

| Unfortunately, the AVR devices do not specify the fuse bytes in the same
| way! So we have to know which device we are generating for.

hex

( low fuse)
.ifdef ckdiv8  0  .else  80  .then
.ifdef ckout   0  .else  40  .then  or
.ifdef sut     sut    .else    %10  .then  4 <<  or
.ifdef cksel   cksel  .else  %0010  .then  or

( high fuse)
0c0  ( base bits)
.ifdef wdton   0  .else  10  .then  or
.ifdef eesave  0  .else  08  .then  or

.def megax4 .def mega328 .or .if
   .ifdef bootsz  bootsz  .else  %00  .then  2*  or
   .ifdef bootrst  0  .else  1  .then  or
.else  ( 48/88/168)
   .ifdef bodlevel  bodlevel  .else  %111  .then  or
.then

( extended fuse)
0f8  ( base bits)
.def megax4 .def mega328 .or .if
   .ifdef bodlevel  bodlevel  .else  %111  .then  or
.else  ( 48/88/168)
   .ifdef bootsz  bootsz  .else  %00  .then  2*  or
   .ifdef bootrst  0  .else  1  .then  or
.then

( Combine the bytes, and store in fuses.)
lohi> lohi>  dup fuses !

( Print the result.)
." Fuse bytes: "
<#  # #  bl hold  # #  bl hold  # #  #> type space

( Calculate lock bits and save in locks.)
0cf  ( base bits)
.ifdef bootrst  %10  .else  %11  .then  4 << or  dup locks !

( Print the result.)
."  Lock byte: "  <#  # #  #> type space