PPM-C412/Configuration
v1.0
www.winsystems.com
Page 31
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
•
485TE - Selects the Transmit Enable signal in RS-422/485 mode; 1=TXD enable,
0=RTS enable
Default = 1 = TXD enable
•
SLEW - Limit slew rate to 250 kbps
Default = 0 = Max data rate
•
TERM - Enables RS-422/485 terminations
Default = 0 = Disabled
•
EN - Enables the SP339 multimode UART
Default = 1 = Enabled
Table 16:
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 17:
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 18:
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)
