CHAPTER 3 – J
u
mpe
r
S
etti
n
g
SPI-6941-LV 31
T
r
a
n
s
mit date co
n
t
r
ol i
n
h
al
f-
d
u
plex mode
In half-duplex mode, the transmission buffer must be controlled to prevent transmit data
from causing a collision. The SPI-6941-LV uses the RTS signal and bit 1 in the modem control
register to control transmit data.
Modem control register
(Setting I/O address +4H) bit 1: 0 … RTS High (Disables transmission)
1 … RTS low (Enables transmission)
S
etti
n
g t
h
e R
S
-
422/R
S
-
485
r
eceive
r
di
s
able co
n
t
r
ol j
u
mpe
r
When the RS-422/RS-485 port is used, the RTS signal is used for driver enable control
Connecting JP1 Pins 4 and 6 disables the receiver at the same time, preventing the port from
receiving output data to an external device.
3
.
3
.
1
R
S
-
422
S
e
tt
i
ng
R
TS
#
J
P
4
:
7
-
8
T
X
D
#
T
X
-
R
TS
-
T
X
+
R
TS+
R
X
+
C
TS+
R
X
-
C
TS
-
J
P
3
:
7
-
8
J
P
3
:
5
-
6
J
P
3
:
3
-
4
J
P
3
:
1
-
2
D
R
D
R
R
X
D
#
R
TS
C
TS
C
OM
2
1
2
3
4
5
6
7
8
9
J
P
4
:
5
-
6
J
P
4
:
4
-
6
120
Ω
120
Ω
120
Ω
120
Ω
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