We are using PORT0 of DS80C400 as DATA0-DATA7 singals. We want to write data using PORT0 to external DAC. We are using Peripheral Chip enable 3 (PCE3 in Port5.7 -> Address: 0x0E00000) Questions: 1)How to write data to Port0? 2)Sample: (Since don't know how to use Port0) char xdata *ADDR; // ADDR is used as PORT0 ADDR = 0x0E00000; // address of PCE3 *ADDR = 0xAA; // data to send We expect Port5.7 (address: 0x0E00000) to be set low (activate low) after the above is 3 command is run. But the Port5.7 did not do anything.
Re-reading all your posts, it becomes increasingly clear that you have a terminology problem there. Contrary to what you write, you're not actually trying to use Port0 as a port. You're planning on memory-mapping that DAC chip. That means you're just using perfectly ordinary memory accesses to external XDATA memory. You seriously need to re-read all the relevant data sheets, and a generic 8051 manual, making sure you actually understand all the terms used in those documents before you proceed. You may even have to re-think the choice of the DS80C400 as your microcontroller.
"You seriously need to re-read ... a generic 8051 manual" That would be the documents commonly referred to as the "bible" for the 8051: Chapter 1 - 80C51 Family Architecture: http://www.semiconductors.philips.com/acrobat/various/80C51_FAM_ARCH_1.pdf Chapter 2 - 80C51 Family Programmer's Guide and Instruction Set: http://www.semiconductors.philips.com/acrobat/various/80C51_FAM_PROG_GUIDE_1.pdf Chapter 3 - 80C51 Family Hardware Description: http://www.semiconductors.philips.com/acrobat/various/80C51_FAM_HARDWARE_1.pdf