Two recent threads suggest that there is some confusion about how to use ATS5xISP to directly connect a PC serial port to Atmel AT89S' devices for ISP purposes.

http://www.8052.com/forum/read.phtml?id=105479 and then
http://www.8052.com/forum/read.phtml?id=105837

For some unknown reason that poster has chosen to go the route of programming through another MCU. With more information, we could have gotten to the root of his connection problems.

The following information is for the benefit of those who want to use ATS5xISP and the (arguably) simpler approach of direct serial port ISP connection. Looking back through support inquiries, issues along the lines of "It doesn't work" usually boil down to:

1. Clipping diodes versus RS-232 line driver/receiver


2. Asserting RESET


3. My connections are different

1. Most users, for their designs, select an RS-232 driver/receiver device with enough paths to accommodate all of the signals. In the program documentation, the illustration of a working PC/ISP connection configuration using clipping diodes is merely an example configuration for cases when the RS-232 driver/receiver device does not have enough paths. An important distinction is that RS-232 driver/receiver devices invert the signals; diodes do not. "Out of the box", the application is configured to match the depicted connection configuration. When DTR and RTS go through an inverting RS-232 driver/receiver, corresponding software changes are required and you've got the source code.

2. In the program documentation, the illustration of a working PC/ISP connection configuration shows the MCU's RESET controlled though a MAX813L Microprocessor Supervisory Circuit. That device's MR# signal, when taken low, drives its RESET output high. When using a RESET connection means that does not invert, corresponding software changes are required and you've got the source code.

3. Connect it how ever you want. Corresponding software changes are required and you've got the source code.

I also get questions like:

1. What C compiler did you use?


2. What do you recommend for a C compiler?

1. As stated in the documentation, I used Microsoft Visual C++ 6.0 Enterprise Edition.

2. If you plan to shell out dollars, I'd go with Microsoft's new VC++ version or Borland C++ Builder 2006. If you plan to go the 'free' compiler route, Microsoft has their Visual C++ 2005 Express Edition http://msdn.microsoft.com/vstudio/e...fault.aspx and Borland offers free V5.5 (Win32 compatible, I think) http://www.borland.com/bcppbuilder/freecompiler/. Plus there's Open Watcom http://www.openwatcom.org/, and the various gcc-based Windows compilers that should compile the code too http://www.bloodshed.net/devcpp.html.