XR88C681CP/40 Exar Corporation, XR88C681CP/40 Datasheet - Page 67

• Manufacturer Part Number: XR88C681CP/40
• Description: Dual Channel UART
• Manufacturer: Exar Corporation

Specifications of XR88C681CP/40

• Features: *
• Number Of Channels: 2, DUART
• Fifo's: 1 Byte, 3 Byte
• Voltage - Supply: 5V
• With Parallel Port: Yes
• With Cmos: Yes
• Mounting Type: Through Hole
• Package / Case: 40-DIP (0.600", 15.24mm)
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

F.2 Output Port Configuration Register (OPCR)
The Output Port pins can be used as General Purpose Output pins, or they can be configured to used in alternate
functions. Table 24 lists the Alternate Functions of each of the Output Port pins.
Many of the Alternate Functions of the various Output Port pins are selected by writing the appropriate data to the OPCR.
The bit format of this register follows
Note: OPCR only addresses the alternate functions for Output Port pins, OP7 - OP2. OP0 and OP1 assume their RTS roles if either
1 = TXRDYB
0 = OPR[7]
Rev. 2.11
Bit 7
OP7
MR1n[7] = 1 or MR2n[5] = 1. Setting those Mode Register bits enables the RTS function. Otherwise, these two ports will only
be General Purpose Output Ports.
Output Port
1 = TXRDYA
0 = OPR[6]
OP0
OP1
OP2
OP3
OP4
OP5
OP6
OP7
Bit 6
OP6
Table 24. Listing of the Alternate Functions for the Output Port
Table 25. Output Port Configuration Register - OPCR
1 = RXRDY/
0 = OPR[5]
FFULLB
Bit 5
OP5
Alternate Function(s)
-
Low for the RTS function.
-
Low for the RTS function.
TXCA_16X Output: Channel A 16X Transmitter Clock Output.
TXCA_1X Output: Channel A 1X Transmitter Clock Output.
RXCA_1X Output: Channel A 1X Receiver Clock Output.
TXCB_1X Output: Channel B 1X Transmitter Clock Output.
RXCB_1X Output: Channel B 1X Receiver Clock Output.
C/T_RDY: The Counter/Timer Ready Output for C/T #1. Note: This output is an
Open-Drain output when used as the Counter/Timer Ready Output.
RXRDY/FFULL_A Output: Channel A Receiver Ready/FIFO Full Indicator. Note:
This is an Open-Drain output for the RXRDY/FFULL_A function.
RXRDY/FFULL_B Output: Channel B Receiver Ready/FIFO Full Indicator. Note:
This is an Open-Drain output for the RXRDY/FFULL_B function.
TXRDY_A Output: Channel A Transmitter Ready Indicator. This is an Open-Drain
output for the TXRDY_A function.
TXRDY_B Output: Channel B Transmitter Ready Indicator. This is an Open-Drain
output for the TXRDY_B function.
RTSA: Request-to-Send (RTS) output for Channel A. Note: This output is Active
RTSB: Request-to-Send (RTS) output for Channel B. Note: This output is Active
1 = RXRDY/
0 = OPR[4]
FFULLA
Bit 4
OP4
67
Bit 3
01 = C/T #1 Output
10 = TXCB (1X)
11 = RXCB (1X)
00 = OPR[3]
OP3
Bit 2
XR88C681
Bit 1
01 = TXCA (16X)
11 = RXCA (1X)
10 = TXCA (1X)
00 = OPR[2]
OP2
Bit 0