This board interfaces the classic ADC0808 8 channel 0-5v ADC to the RCbus interface. In addition it provides digital inputs. Whilst it is a general purpose board the primary goal and reason for the digital inputs is to link to the various cheap analog joystick type controllers that are available.

Jumpers select the port range between 0x40 and 0x70 for the ADC and 48-78 for the digital input and completion status. Other jumpers control whether to use a cystal or the main system clock as the ADC clock, and a divider option to divide the clock down into the range ADC requires. For the usual RC2014 style 7.37MHz the divider is sufficient. At 18.432 MHz you'll need to populate X1.

Operation is fairly simple. Out to the port base plus the channel number, wait for completion and read back. Although there are 8 channels there is only one actual latched value so the result reads back on all 8 ports.