Acces ICOM-2S, User Manual

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3-1
Manual MICOM-2S.Eb
Figure 3-1: Simplified Schematic
Chapter 3: Option Selection
The following paragraphs describe the functions of the various jumpers on the ICOM-2S card. Refer
to the Figure 3-2, Option Selection Map for the locations of these jumpers on the card.
CTS
The CTS bit is used to indicate that the device connected to the ICOM-2S is ready to accept data from
the ICOM-2S. Status can be tested by reading bit 4 of the MSR(modem status register) from the
UART. The CTS line does not affect the operation of the card.
Terminations and Bias
A transmission line should be terminated at the receiving end in its characteristic impedance. Installing
a jumper at the location labeled LD applies a 136
?
load across the input for RS422 mode and across
the transmit/receive input/output for RS485 operation. When noise is a potential problem on long
lines, the terminating resistor should be divided and its center point grounded to help reduce noise
voltage pickup. To accomplish this, also install a jumper at the position marked LD GND for 68-ohm
termination resistance on the positive and negative branches of the receiving line.
In RS485 operations, where there are multiple terminals, only the RS485 ports at each end of the
network should have terminating resistors as described above. If the card is to have an ungrounded
load, do as above except do not install the
LDGND jumper. (See Appendix A,
Application Considerations.) Also, for RS485
operation, there must be a bias on the RX+ and
RX- lines. If the ICOM-2S card is to provide
that bias, install jumpers at the locations
lBIAS and -BIAS.
RTS Control
For RS485 operation, installing a jumper at the
location labeled RTS allows the state of the
RTS line to be controlled by the UART. Either
this jumper, or the AUTO (A/B) jumper, must
be installed.
Auto (A/B)
Allows the ACE data buffer to automatically
control the transmitter drivers. When operating
with Windows programs, use the Auto mode.