XR88C681J-F Exar Corporation, XR88C681J-F Datasheet - Page 58

• Manufacturer Part Number: XR88C681J-F
• Description: IC UART CMOS DUAL 44PLCC
• Manufacturer: Exar Corporation
• Type: CMOS Dual Channel UARTr

Specifications of XR88C681J-F

• Number Of Channels: 2, DUART
• Package / Case: 44-LCC (J-Lead)
• Features: *
• Fifo's: 1 Byte, 3 Byte
• Voltage - Supply: 5V
• With Parallel Port: Yes
• With Cmos: Yes
• Mounting Type: Surface Mount
• Data Rate: 1 Mbps
• Supply Voltage (max): 5.25 V
• Supply Voltage (min): 4.75 V
• Supply Current: 15 mA
• Maximum Operating Temperature: + 85 C
• Minimum Operating Temperature: - 40 C
• Mounting Style: SMD/SMT
• Operating Supply Voltage: 5 V
• Propagation Delay Time Ns: 400 ns
• No. Of Channels: 2
• Supply Voltage Range: 4.75V To 5.25V
• Operating Temperature Range: -40°C To +85°C
• Digital Ic Case Style: PLCC
• No. Of Pins: 44
• Filter Terminals: SMD
• Rohs Compliant: Yes
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant, Lead free / RoHS Compliant
• Other names: 1016-1329

Figure 30 shows that the phase relationship between the Receiver’s sampling point and each serial data bit is changing.
In this case, the Receiver is sampling each serial data bit, earlier and earlier in the bit period, with each successive data
bit. This phenomenon is known as receiver drift. If there is no correction for receiver drift, there will be many errors in the
transmission and reception of this serial data, as depicted in Figure 31.
Figure 31 shows the Receiver sampling an eight bit string of data with bit pattern 0101010. It is interesting to note that, in
Figure 31, the Receiver sampled 01010010. It should be noted that Receiver drift can also be a problem is the local
Receiver is slower than the remote Transmitter clock.
Received Data
Rev. 2.11
Actual Data
Figure 30. Receiver (1X) Sampling, if the RX Clock is Slightly Faster Than the TX Clock
0
0
Figure 31. Illustration of an Error due to Receiver Drift
1
1
0
0
1
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1
0
0
0
1
1
0
0
1
1