Figure 6. Simplified RS-422/485 Schematic
When a port has this option, additional circuitry will be mounted to the main board. The standard 232D4SS8 comes with the RS-485 option on four ports (Port A-D). Use Figure 2 to locate its position.
Refer to Table 5 for pin-out, signal name, and signal direction information. Also, refer to Figure 6 for a simplified schematic showing the relationship between the Master port and a port configured with the RS-422/485 option.
NOTE: This option only supports transmit and receive data signals (TD & RD) from the Master port.
RS-422/RS-485 Mode
The model 232D4SS8 comes standard with an automatic send data (SD) control of the RS-485 driver. SD control automatically enables the RS-485 driver by sensing the leading edge of the first character transmitted from the device connected to the Master port. After the last character transmits, the send data timer circuit waits one character time (about 1 millisecond at 9600 baud) before disabling the RS-485 driver.
Documentation Number 232D4SS84502 Manual | 11 |
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