Do realize that SD card does not have "drive firmware".
I realize no such thing, because they do
have "drive firmware"
SD cards are removable drives, and all
current drives have onboard controllers and firmware.
In the case of SD cards, the controller is usually a modified 8051 CPU or an ARM variant.
See On MicroSD Problems « bunnie's blog for some interesting hacking of SD cards and onboard controllers.
And the firmware on SD cards attempts to do wear leveling, so my comments about number of times a call can be written to and overall drive life stand.