Analogue Control Interface

FX839

© 1997 Consumer Microcircuits Limited

8

D/839/4

ADC DATAx' command. If this is not done, then the converted data returned on 'C-BUS' will be the result of the

previous conversion on the selected channel. It is possible for the data conversion rate to exceed the reply rate

on 'C-BUS'. In such a case, the data returned will be the result of the most recent conversion completed.

Figure 3: Example of a "conversion and read"

and the clock divider.

Note that after reading the ADC1 data, it is necessary to re-enable the conversion of data by setting Bit 5 of the

ADC Control Register to ‘1’.

Magnitude Comparators and Interrupt Request

High and low digital comparator reference levels are provided for the four digital magnitude comparators via the

'C-BUS' interface. The digital input to the comparators is provided by the most significant 8 bits of each ADC

data.

When the sampled data falls outside the high or low digital comparator reference levels the status register is

updated and the IRQN pin is pulled low. When a reference level is set to '0', its IRQ is disabled.

1.5.1

Software Description

Address/Commands

Instructions and Data are transferred via the 'C-BUS' in accordance with the timing information given in

Figure 4.

Instruction and data transactions to and from the FX839 consist of an Address/Command byte followed

by either:

(i)

a control or DAC data write (1 or 2 bytes) or,

(ii)

a status or ADC data read (1 or 2 bytes)