PCM-C418/Configuration
v1.0
www.winsystems.com
Page 23
selectable from 50 through 115.2 kbps. Individual modem handshake control signals
are supported for all ports.
COM1 and COM2 Configuration Options in BIOS
The PCM-C418 uses SP339 multi-mode transceivers, which include RS-232, RS-485,
and RS-422 capability in a single device. When RS485 or RS422 modes are selected in
the BIOS, a secondary configuration option for selecting the transmitter enable method
appears. TXD is the default setting, which automatically toggles the RTS bit when data
is in the transmit buffer. The second BIOS option is RTS, and requires that the UART
RTS bit be toggled prior to data transmission in RS-422 or RS-485 modes.
•
RS-232 mode
•
RS-422 mode with RTS transmitter enable - (TX Direction = RTS)
•
RS-422 mode with auto transmitter enable - (TX Direction = TXD)
•
RS-485 mode with RTS transmitter enable - (TX Direction = RTS)
•
RS-485 mode with auto transmitter enable - (TX Direction = TXD)
Additional COM1 and COM2 Configuration Options
The SP339 transceivers include RS-422/485 termination and SLEW control. These
settings are disabled by default and can be enabled/disabled by writing to the
appropriate mode control registers identified below.
UART Mode Controls
UART 1-2 Mode Controls (DEVFUN=0x00)
Default = 0x05 = RS232 Enabled
Table 11:
Register (0x1E9) for device/function selection
Device/Function Register Window at 0x1E9
Device
Function
DEVFUN
Description
0
0
0x00
UART 1-2 mode controls
0
1
0x01
UART 3-4 mode controls
Table 12:
Register (0x1EA) for COM1
D7
D6
D5
D4
D3
D2
D1
D0
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
X
X
485TE
SLEW1
TERM1
EN1
UART1 mode (0-3)
Table 13:
Register (0x1EB) for COM2
D7
D6
D5
D4
D3
D2
D1
D0
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
X
X
485TE
SLEW2
TERM2
EN2
UART2 mode (0-3)
