CD2231

Manufacturer Part NumberCD2231
DescriptionCD2231 Intelligent Two-channel Lan And Wan Communications Controller
ManufacturerIntel Corporation
CD2231 datasheet
 
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Intelligent Two-Channel LAN and WAN Communications Controller — CD2231
Bits 3:0
FIFO Threshold in characters
Note that the maximum value allowed for this field is 12 (0C hex). This 4-bit binary
encoded field, sets the FIFO transfer threshold for both transmit and receive FIFOs
for both Interrupt and DMA Transfer modes.
In Asynchronous mode, a Good Data transfer is initiated for the number of charac-
ters in the FIFO greater than the specified threshold. Receive timeout and the occur-
rence of a receive data exception are also cause to initiate a receive transfer. In
Synchronous modes, data transfer is initiated when the number of characters in the
FIFO is greater than the specified threshold. An end of frame also initiates a receive
transfer.
For transmit operation, the CD2231 attempts to refill the transmit FIFO when the
empty space in the FIFO is greater than the set threshold. In synchronous frame
transmissions, the CD2231 stops refilling the transmit FIFO once the last character
in the frame transfers to the FIFO.
8.2.6
Channel Option Register 5 (COR5)
Register Name: COR5
Register Description: Channel Option Register 5
Default Value: x’00
Access: Byte Read/Write
Bit 7
Bit 6
Bit 5
DSRod
CDod
CTSod
This register is used to define the current-state change options to be monitored.
Bit 7
DSRod = 1
Detect zero-to-one transition on DSR* input (one-to-zero transition of DSR
(MSVR) bit)
Bit 6
CDod = 1
Detect zero-to-one transition on CD* input (one-to-zero transition of CD (MSVR)
bit)
Bit 5
CTSod = 1
Detect zero-to-one transition on CTS* input (one-to-zero transition of CTS (MSVR)
bit)
Bit 4
In/Out – Automatic receive flow control select
This bit is ignored when bits 3:0 are all zeros.
0 = Use out-of-band flow control (DTR pin).
1 = Use in-band flow control (automatic transmission of XOFF/XON characters)
Bit 4
Datasheet
Bit 4
Bit 3
In/Out
Number of characters in FIFO
0
Less than or equal to threshold
0
Greater than threshold
1
Less than or equal to threshold
1
Greater than threshold
Intel Hex Address: x’17
Motorola Hex Address: x’14
Bit 2
Bit 1
Bit 0
Rx flow control threshold
CD2231 Action
DTR asserted
DTR deasserted
XON transmitted
XOFF transmitted
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