CD2231 Intel Corporation, CD2231 Datasheet - Page 99

• Manufacturer Part Number: CD2231
• Description: CD2231 Intelligent Two-channel Lan And Wan Communications Controller
• Manufacturer: Intel Corporation

8.2.6
Datasheet
Register Name: COR5
Register Description: Channel Option Register 5
Default Value: x’00
Access: Byte Read/Write
DSRod
Bit 7
Bits 3:0
Channel Option Register 5 (COR5)
This register is used to define the current-state change options to be monitored.
Bit 7
Bit 6
Bit 5
Bit 4
CDod
Bit 6
Intelligent Two-Channel LAN and WAN Communications Controller — CD2231
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.
DSRod = 1
Detect zero-to-one transition on DSR* input (one-to-zero transition of DSR
(MSVR) bit)
CDod = 1
Detect zero-to-one transition on CD* input (one-to-zero transition of CD (MSVR)
bit)
CTSod = 1
Detect zero-to-one transition on CTS* input (one-to-zero transition of CTS (MSVR)
bit)
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)
CTSod
Bit 5
Bit 4
0
0
1
1
Less than or equal to threshold
Greater than threshold
Less than or equal to threshold
Greater than threshold
In/Out
Number of characters in FIFO
Bit 4
Bit 3
Rx flow control threshold
Bit 2
Motorola Hex Address: x’14
XOFF transmitted
XON transmitted
DTR deasserted
CD2231 Action
Bit 1
DTR asserted
Intel Hex Address: x’17
Bit 0
99