Omega Engineering CIO-DAC08, CIO-DAC16 user manual Register Architecture, Control & Data Registers

4 REGISTER ARCHITECTURE

The CIO-DAC## is a simple board to understand. All control and data is read/written with simple I/O read and write commands. No interrupt or DMA control software is required. Thus, the board's functions are easy to control directly from BASIC, C or PASCAL.

4.1 Control & Data Registers

The CIO-DAC16 has 32 analog output registers, the CIO-DAC08 has 16. There are two registers for each channel; one for the lower 8 bits and one for the upper 4 bits.

The first address, or BASE ADDRESS, is determined by the setting of a bank of switches on the board.

The register descriptions all follow the format:

7	6	5	4	3	2	1	0
D5	D6	D7	D8	D9	D10	D11	D12

Where the numbers along the top row are the bit positions within the 8 bit byte and the numbers and symbols in the bottom row are the functions associated with that bit.

To write to or read from a register in decimal or HEX, the following weights apply:

Table 4-1. Register Bit Weights

BIT POSITION	DECIMAL VALUE	HEX VALUE
0	1	1
1	2	2
2	4	4
3	8	8
4	16	10
5	32	20
6	64	40
7	128	80

To write a control word or data to a register, the individual bits must be set to 0 or 1 then combined to form a byte. Data read from registers must be analyzed to determine which bits are on or off.

The method of programming to set or read bits from bytes is beyond the scope of this manual. It is covered in most Introduction To Programming books, available from a bookstore.

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