Measurement Computing PPIO-DIO24H - Manual (Page 11)

Table 4-1. 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 a control word or data to a register, the individual bits must be set to 0 or 1
then combined to form a byte.
The method of programming required to set/read bits from bytes is beyond the scope
of this manual. It is covered in most Introduction To Programming books.
In summary form, the registers and their function are listed on the following table.
Each register has eight bits which can constitute a byte of data or can be eight
individual bit set/read functions.
Table 4-2. Register Functions
Configure None. No read back. 3
Port C Outputs Port C Inputs 2
Port B Outputs Port B Inputs 1
Port A Outputs Port A Inputs 0
WRITE FUNCTION READ FUNCTION ADDRESS
4.4 DIGITAL I/O REGISTERS
PORT A DATA
A0 A1 A2 A3 A4 A5 A6 A7
0 1 2 3 4 5 6 7
PORT B DATA
B0 B2 B2 B3 B4 B5 B6 B7
0 1 2 3 4 5 6 7
Ports A & B can be programmed as input or output. Each is written to and read from
in bytes. For control and monitoring purposes, individual bits are usually used. Mask
unwanted bits out of reads and writes.
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