USB-based Loader circuit for DS89C4x0

Here's an alternative flash loader/programmer circuit for Maxim's DS89C4x0 microcontrollers. Most of the circuit parts came from a cheap Nokia data cable bought at CDR-King.

from the conventional "Serial Load Hardware Configuration":
to this one:*uses PL2303 from this cable: CHEAP USB-serial interface cable for our MCU projects!
*completely USB-powered
*no other addtional IC (e.g 74xx125)
**but still need to place the external crystal on the DS89C4x0

inside the cdrking's nokia data cable:
connections (tapping of wires):
actual circuit:*has a pull-up on P3.7 pin (only for some batches of ds89c420 as indicated in their errata)

the 40-pin DIP DS89C420 (obsolete part):
the MTK (Loader software):*the actual hardware is not working with version 2.4.10
*works also with Loader420 and hyperterminal..
dalsemi.com/microcontroller/dev_tool_software/mtk/obsolete/

demo ("classic" LED blinker program):

SDCC code:Compiled using M-IDE with SDCC