Measurement Computing CIO-DAS08-AOH - Manual (Page 13)

6 CIO-DAS08-AOx ARCHITECTURE
All of the programmable functions of the CIO-DAS08-AOx are accessible through the control and data registers, which are
explained here.
6.1 REGISTER LAYOUT
The CIO-DAS08-AOx is controlled and monitored by writing to and reading from 16 consecutive 8-bit I/O addresses. The
first address, or BASE ADDRESS, is determined by setting a bank of switches on the board.
Register manipulation is best left to experienced programmers as most of the possible functions are implemented in easy to
use Universal Library™.
The register descriptions use the following format:
CH1 CH2 CH4 CH8 A/D12
LSB
A/D11 A/D10 A/D9
0 1 2 3 4 5 6 7
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 hexadecimal, the bit weights in Table 6-1 apply:
Table 6-1. Byte Bit Weights
80 128 7
40 64 6
20 32 5
10 16 4
8 8 3
4 4 2
2 2 1
1 1 0
HEX VALUE DECIMAL VALUE BIT POSITION
To write control words 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 required to set/read bits from bytes is beyond the scope of this manual. It will be covered in
most Introduction To Programming books, available from a bookstore.
In summary form, the registers and their function are listed on Table 6-2. Within each register are eight bits which may
constitute a byte of data or they may be eight individual bit set/read functions.
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