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PC ↔ 422/485 SERIAL INTERFACE
E1 selects IRQ3; at position 4, IRQ4 is selected. If no IRQ is
required, remove the jumper completely.
If you've set DIP switch S1's position 8 CLOSED to select the
address COM1:, you must set this jumper to IRQ4. If you've set
S1's position 6 CLOSED to select the address COM2:, you must set
this jumper to IRQ3.
E2 Header E2 selects whether the RS-485 driver is enabled by the
UART signal Request To Send (RTS) or always enabled. With the
jumper installed, RTS enables the driver. Removing the jumper
enables the driver regardless of RTS. (Please be aware that echo is
not disabled in 2-wire RS-485 operation.)
RS-422:
driver/receiver pair is installed at U6 (75176) and U7 (75174) and
Header E2 is removed or set to one pin.
RS-485:
are installed at U6 (75176) and U7 (75174). The output of the
RS-422/485 driver is capable of being Active (enabled) or Tri-State
(disabled) for RS-485 compatibility. Header E2 selects whether the
RS-485 driver is enabled by the SCC signal Request To Send
(RTS) or always enabled. With the jumper installed at Header E2,
RTS enables the driver (RS-485). Removing the jumper from
Header E2 enables the driver regardless of RTS (RS-422).
12
The RS-422 option is selected when the RS-422/485
The RS-485 option is installed when the RS-422/485 chips
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