B&B Electronics RS-485 manual Set Digital Output States, Digital I/O Mask Values

Table 5.1 - Digital I/O Mask Values

	Mask Values
I/O Line	Hexadecimal	Decimal
Digital Output #0	1H	1
Digital Output #1	2H	2
Digital Output #2	4H	4
Digital Input #0	8H	8
Digital Input #1	10H	16
Digital Input #2	20H	32

Example 5.2 - Determining the status of Digital Input #1 of the module with and address of 10.

mask = &H10

Command$ = “!” + CHR$(addr) + “RD” Print #1, Command$;

Reply$ = INPUT$ (1, #1) states = ASC (Reply$) status = states AND mask

If status is equal to zero then Digital Input #1 is LOW. If status is not equal to zero then Digital Input #1 is HIGH.

Set Digital Output States

The Set Digital Output command is used to set the states of the 3 digital output lines. This command requires a data byte. The data byte is used to specify the output states. Bits 0-2 correspond to the states of digital outputs 0-2. If a bit is a 0 then the output will be set LOW. If a bit is a 1 then the output will be set HIGH. NOTE: This command ignores Bits 3-7 of the data byte.

The steps to setting the digital output states are given below:

1)Constructing the command string:

a)Set Appropriate Outputs HIGH states = states OR mask

By “ORing” the current states with the appropriate mask of a digital output (given in Table 5.1), the output’s data bit will be set to a “1” (which will be set HIGH).

24 485SDA103798 Manual

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