Rs-485 Half-Duplex Mode; Using The Rs-232 Link In Receive-Only Mode - Campbell SDM-SI01A Product Manual

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Enabling handshaking will increase active current consumption due to the extra RS-232 load. It

will not affect sleep current, however, as the RS-232 chip is disabled (sleep is set by calling the

SerialClose()

function).

For connection diagrams and further information on using handshaking, consult

examples for connecting the SDM-SIO1A

NOTE:

Auto flow control should only be selected in RS-232 mode.

When Auto flow control is enabled, the user cannot set or clear the spare I/O ports

(pins 8 and 11).

7.1.2 RS-485 half-duplex mode

In RS-485 half-duplex mode, the SDM-SIO1A will wait for approximately 2.5 ms after a character

is received before it tries to transmit any data in its transmit buffer. This is to ensure that a

contention does not occur on the data line which will cause data corruption. There is also a delay

of at least the time to send one character after the last character has been transmitted before the

SDM-SIO1A will listen for new incoming data.

NOTE:

When in either RS-485 half-duplex or full-duplex modes, the user cannot set or clear the

spare I/O ports (pins 8 and 11).

To place the SDM-SIO1A into RS-232 receive-only mode, use the SerialOpen() instruction

with the SerialOpenFormat value set within the range of 64 to 79. Consult

for more detailed information about these settings.

In receive-only mode, the SDM-SIO1A will consume less current than normal but still can receive

new information on its RS-232 port.

The following example will set the SDM-SIO1A with address 0 into receive-only mode. All normal

baud rates and buffer sizes are supported.

Example

SerialOpen

(32,115200,64,100,10000) 'Set receive only mode

(p. 13).

SDM-SIO1A and SDM-SIO4A Serial Input/Output Modules

Wiring

SerialOpen()

(p. 18)

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