Publication No. 500-9300527837-000 Rev. A.0
FPGA Registers 77
6.59 COM Port Mode Register (0x6BC)
6.60 COM Port RS485 Auto Direction Control Register (0x6BD)
When Auto Direction Control is enabled, it causes the RTS signal to assert and
enable the transceiver whenever there is data ready to be transmitted on the port.
Otherwise, the transceiver is tri-stated.
NOTE
Auto Direction Control for a COM port can only be enabled when the corresponding transceiver is in
RS422 mode.
6.61 COM Port Loopback Enable Register (0x6BE)
Test software can use loopback mode to test the basic functionality of the
transceiver.
Bits
Read/Write Description
Default
7 to 2
Read only
COM8 to COM3 mode:
COM8 to COM3 are not available
000000
b
1
Read/Write COM2 mode:
1 = COM2 transceiver in RS422 mode
0 = COM2 transceiver in RS232 mode
0
0
Read/Write COM1 mode:
1 = COM1 transceiver in RS422 mode
0 = COM1 transceiver in RS232 mode
0
Bits
Read/Write Description
Default
7 to 2
Read only
COM8 to COM3 Auto Direction Control mode:
COM8 to COM3 are not available
000000
b
1
Read/Write COM2 RS485 Auto Direction Control mode:
1 = COM2 RS485 Auto Direction Control enabled
0 = COM2 RS485 Auto Direction Control disabled
0
0
Read/Write COM1 RS485 Auto Direction Control mode:
1 = COM1 RS485 Auto Direction Control enabled
0 = COM1 RS485 Auto Direction Control disabled
0
Bits
Read/Write Description
Default
7 to 2
Read only
COM8 to COM3 loopback enable:
COM8 to COM3 are not available
000000
b
1
Read/Write COM2 loopback enable:
1 = COM2 transceiver loopback mode enabled
0 = COM2 transceiver loopback disabled (normal operation)
0
0
Read/Write COM1 loopback enable:
1 = COM1 transceiver loopback mode enabled
0 = COM1 transceiver loopback disabled (normal operation)
0