DAN-173 Datasheet, PDF (3/3 Pages) Exar Corporation – UPGRADING FROM XR88C681 TO XR88C92/192

DATA COMMUNICATIONS APPLICATION NOTE
DAN173
3.7 BAUD RATE TABLES
There are four baud rate tables available in the C681 and six baud rate tables available in the C92/192.
The parameters that select the baud rate table and decide the baud rate in the C681 are:
1. CSR bits 7:4 for RX clock and CSR bits 3:0 for TX clock
2. ACR bit-7
3. Set RX BRG Select Extend bit for RX clock
4. Set TX BRG Select Extend bit for TX clock
The parameters that select the baud rate table and decide the baud rate in the C92/192 are:
1. CSR bits 7:4 for RX clock and CSR bits 3:0 for TX clock
2. ACR bit-7
3. MR0A bit-0 for Extended Baud Rate Table 1
4. MR0A bit-2 for Extended Baud Rate Table 2
The first two parameters are identical for the C681 and the C92/192. The remaining parameters result in differ-
ent baud rates. Please refer to the datasheets for a complete listing of baud rates.
4.0 SUMMARY
For direct drop-in replacement of the XR88C681 by the XR88C92 or the XR88C192, the following conditions
must be satisfied:
• 44-PLCC package is used
• 5V VCC is used
• Z-mode is not used
• MISR is not used
• Extended baud rate selection is not used
• Stand-by mode is not used
Otherwise, hardware and/or software changes are required.
NOTICE
EXAR Corporation reserves the right to make changes to the products contained in this publication in order to
improve design, performance or reliability. EXAR Corporation assumes no responsibility for the use of any cir-
cuits described herein, conveys no license under any patent or other right, and makes no representation that
the circuits are free of patent infringement. Charts and schedules contained here in are only for illustration pur-
poses and may vary depending upon a user’s specific application. While the information in this publication has
been carefully checked; no responsibility, however, is assumed for inaccuracies.
EXAR Corporation does not recommend the use of any of its products in life support applications where the
failure or malfunction of the product can reasonably be expected to cause failure of the life support system or
to significantly affect its safety or effectiveness. Products are not authorized for use in such applications unless
EXAR Corporation receives, in writing, assurances to its satisfaction that: (a) the risk of injury or damage has
been minimized; (b) the user assumes all such risks; (c) potential liability of EXAR Corporation is adequately
protected under the circumstances.
Copyright 2004 EXAR Corporation
January 2004
Send your UART technical inquiry with technical details to hotline: [e-mail]
Reproduction, in part or whole, without the prior written consent of EXAR Corporation is prohibited.
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