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Serial Ports
The EPM-19 includes four on-board 16550-based serial channels located at standard PC I/O
addresses. Each COM port can be independently enabled or disabled in the BIOS Setup utility.
All four COM ports by default are set to RS-232 mode
COM1 and COM2 are RS-232 (up to 115.2K baud) serial ports. There are no configuration
jumpers for COM1 and COM2 because they only operate in RS-232 mode. IRQ lines are
chosen in the BIOS Setup utility.
COM3 and COM4 can be operated in RS-232 or RS-422/485 mode. IRQ lines are chosen in
the BIOS Setup utility, but software configuration is required to set the COM3 and COM4
transceivers to RS-422/485 mode.
Additional non-standard baud rates are also available through the BIOS Setup utility.
COM3/COM4 H
Refer to the EPM-19 Hardware Reference Manual for information on the settings for jumper
block V1 required for using COM3 and COM4 in RS-422/485 modes.
COM3/COM4 S
By default, COM3 and COM4 are configured for RS-232 operation. Two registers in the
Vortex86DX2 (0x9A and 0x7A) need to be programmed for COM3 and/or COM4 to operate in
RS-422 or RS-485 mode. Table 23 and Table 24 provide bit-level descriptions of these registers.
Note that there is also a register setting in the FPGA that should be configured when using RS-
422 mode (the default assignment supports RS-232 and RS-485 operating modes). Refer to the
section titled COM Port Register on page 19.
To configure COM3 and COM4 for RS-422/485 Mode
1.
Write 0xFF to I/O register 0x9A (sets GPIO-P2[7:0] to outputs)
2.
Write 0x0E to I/O register 0x7A (disables RS-232 mode and enables transceivers)
To reconfigure COM3 and COM4 for RS-232 Mode
1.
Write 0xFF to I/O register 0x9A (sets GPIO-P2[7:0] to outputs)
2.
Write 0x02 to I/O register 0x7A (enables RS-232 mode and enables transceivers)
EPM-19 Programmer's Reference Manual
C
ARDWARE
ONFIGURATION
C
OFTWARE
ONFIGURATION
Programming Information for Hardware Interfaces
26
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