AC37 High-Speed Communication Adapter Card
REGISTER DEFINITION
2-6
LINE CONTROL REGISTER:
OFFSET 3 - READ/WRITE
This register is used to select the format of serial communications data. The bits in the Line Control Register are
defined as such:
Bits 0 and 3:
Word Size Select
These two bits specify the number of bits in each serial character sent or received. The
AC37 does not support all of the various word sizes that the 16,550 UART does, but the
most commonly used data formats are supported and are selected using the settings
shown below:
Bit 1:
Not Used
Bit 2:
Not Used
Bit 4:
Address-/Data Select
This bit controls the state of the 9th data bit when the 9 bit mode is selected. When
communicating to a Remote I/O brick using binary protocol, this bit determines if the
next byte written to the transmit FIFO will be interpreted as an address or data byte. If
bit 4 is set to a logic 0, the 9th bit of data written to the transmit FIFO will be set to a
logic 1 when transmitted, and will be interpreted as an address byte by the Remote I/O.
Conversely, if bit 4 is set to a logic 1, the 9th bit of data written to the transmit FIFO will
be set to a logic 0 when transmitted and interpreted by the Remote I/O as data bytes.
Bit 5:
Not Used
Bit 6:
IRQ Output Control
This bit controls the state of the Remote Bus IRQ line. When bit 6 is set to a logic 1, the
IRQ line of the Remote Bus is activated. When bit 6 is set to a logic 0, the IRQ line will
be put into receive mode.
Bit 7:
DLAB Control
This bit is used to control access to the Baud Rate Select Register. If this bit is set to a
logic 0, the Receive buffer, Transmit buffer, and Interrupt Enable register may be
accessed. If this bit is set to a logic 1, only the Baud Rate Select register may be
accessed at offset 0.
Bit 3
Bit 0
Format
1
1
9 Data Bits, 1 Stop Bit *
0
1
8 Data Bits, 1 Stop Bit **
1
0
7 Data Bits, 1 Parity Bit, 1 Stop B
(Parity will always be even)
0
0
Reserved
* 9 Bit mode is used to communicate to Remote I/O using
binary protocol.
** 8 Bit mode is used to communicate to Remote I/O
using ASCII protocol.
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