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Command List:
=============
'i' ... identify
'b' ... boot
'r' ... reset
'f' ... read flash
'F' ... write flash
'e' ... read eeprom
'E' ... write eeprom
'c' ... read config
'C' ... write config
Description:
------------
Every command consits of one byte command code, a fixed number of bytes as
arguments and ends with a XOR checksum over all bytes sent. All data is
transferred LSB first.
Every answer to a command starts with the command code. One byte return value,
optionally some data and a checksum (XOR over all bytes received)
The return codes have the following meaning:
code | Error
------+-------------
0 | OK
1 | invalid command
2 | bad checksum
3 | not implemented
4 | flash write error
5 | address invalid
6 | address prohibited
identify:
~~~~~~~~~
command:
'i' | <csum> (in this case <csum> will always be 'i')
answer:
'i' | <ret> | version | name | devid | fss | supported | <csum>
version:
2bytes, protocol version
It is an error if the major version (MSB) is different (hence any
protocol update must change the major version of the bootloader).
name:
10bytes, a descriptive name of the device.
The downloader has to compare this name with the device name supplied
via commandline and stop in case they don't match
devid:
2bytes, device id of the PIC
The downlaoder may use this id to check if it talks to the right bootloader
fss:
1byte, flash segment size
The number of words of one flash segment which has to be written at once.
The downloader can fill up holes by supplying the illegal code word 0xFFFF
for some addresses. The bootloader will skip those areas.
supported:
1byte, a bitmap showing supported commands
The commands 'identify' and 'boot' are always supported by the bootloader,
others may not (i.e.: not all PICs allow to update the configurtion words)
bit | command
-----+----------
0 | reset
1 | read flash
2 | write flash
3 | read eeprom
4 | write eeprom
5 | read config
6 | write config
boot:
~~~~~
command:
'b' | <csum> (in this case <csum> will always be 'b')
answer:
'b' | <ret> | <csum>
This instucts the bootloader to boot to the user application directly (no reset)
reset:
~~~~~~
command:
'r' | <csum> (in this case <csum> will always be 'r')
answer:
'r' | <ret> | <csum>
The device performs a reboot. If the boot condition (i.e.: port pin) is not met
this instructs the device to boot to the user application.
read flash:
~~~~~~~~~~~
command:
'f' | addr | <csum>
answer:
'f' | <ret> | data | <csum>
The bootloader reads <fss> words from flash address <addr> and returns it as
<data>.
write flash:
~~~~~~~~~~~~
command:
'F' | addr | data | <csum>
answer:
'F' | <ret> | <csum>
The bootloader writes <data> (which has to contain exactly <fss> words) to address
<addr> inside the flash.
read eeprom:
~~~~~~~~~~~~
command:
'e' | addr | len | <csum>
answer:
'e' | <ret> | data | <csum>
The bootloader reads <len> bytes from eeprom at address <addr> and returns it as
<data>.
write eeprom:
~~~~~~~~~~~~~
command:
'E' | addr | len | data | <csum>
answer:
'E' | <ret> | <csum>
The bootloader writes <data> (which has to contain exactly <len> bytes) to address
<addr> inside the eeprom.
read config:
~~~~~~~~~~~~
command:
'c' | nr | <csum>
answer:
'c' | <ret> | word | <csum>
The bootloader reads and returns the configuration word number <nr>.
write config:
~~~~~~~~~~~~~
command:
'C' | nr | word | <csum>
answer:
'C' | <ret> | <csum>
The bootloader writes <word> onto configuration word number <nr>.
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