COM1 - RS- 485
Page 2 - 10
OPERATIONS MANUAL LBC-Plus
991206
WinSystems - "The Embedded Systems Authority"
1 2 3
o o o
1 2 3
o o o
U3 - Not In stalled
U4 - In stalled
U8 - Not In stalled
1 o o 6
2 o o 7
3 o o 8
4 o o 9
5 o
J8
J10
COM1 DB9
N/C
TX/RX+
TX/RX-
N/C
GND
N/C
N/C
N/C
N/C
VCC
R8
R9
R10
TX/RX+
TX/RX-
RS- 485 NOTE : Be cause RS- 485 uses a sin gle
twisted- pair, all trans mit ters are con nected in par al -
lel. Only one sta tion at a time may trans mit or have
its trans mit ter en abled. The trans mit ter En able/Dis -
able is con trolled in soft ware us ing bit 1 in the Mo -
dem Con trol Reg is ter (RTS). When RTS is set, the
trans mit ter is en abled, and when cleared (the nor mal
state) the trans mit ter is dis abled and the re ceiver is
en abled. Note that it is nec es sary to al low some
mini mal set tling time af ter ena bling the trans mit ter
bef ore trans mit ting the first char ac ter. Like wise, fol
-
low ing a trans mis sion, it is nec es sary to be sure that
all char ac ters have been com pletely shifted out of
the UART (Check Bit 6 in the Line Status Reg is ter)
bef ore dis abling the trans mit ter to avoid chop ping
off the last char ac ter.
