Solution:

Basically, two PCL-816-DA-1 modules can't be used simultaneously due to their "high power consumption". The PCL-816 processes only one module at a time. But, Register Base+15 must first be set correctly in user's program to activate the required module. For example, to activate the module installed in slot 1, you have to write data '1' to BASE+15. If user want to activate the module in slot 2, write data '2' to BASE+15. Anyway, each PCL-816 just can add-on ONE PCL-816-DA-1 module. But you can use TWO PCL-816 card in one PC. Then user got FOUR High Resolution D/A channels. If user don't need the A/D convert function, the PCI-1720 just can meet your needs.