National Instruments PCMCIA Serias, Начало работы

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Chapter 4 Using Your Serial Hardware
© National Instruments Corporation 4-3
PCMCIA Serial for Windows 98/95
Setting the Transceiver Control Mode
The recommended method for setting the transceiver control mode is with
the serial configuration utility located in the Windows 98/95 Device
Manager. For more information, refer to the
Communication Port Settings
section in Chapter 3, Configuration . The mode you select in the Device
Manager is automatically configured when you open a port on a serial
interface. You can also set the hardware transceiver control mode from
within a DOS application. For each port you want to control, write the
control byte for the mode you want to select to the scratch register of the
UART. Table 4-2 shows the control bytes for each mode.
The scratch register is located at offset 7 from the base address of the port.
For example, if COM2 were located at base address 0x3F8, and you wanted
to set the PCMCIA-485 board to two-wire mode with DTR control, you
would write a 0x02 to I/O address 0x3FF. The PCMCIA-485 board would
immediately switch to the two-wire mode with DTR control.
Table 4-2. Transceiver Mode Control Bytes
Transceiver Mode Control Byte
Four-wire mode 0x00
Two-wire mode: DTR with echo 0x01
Two-wire mode: DTR controlled 0x02
Two-wire mode: TXRDY auto control 0x03