IT8761E [ETC]
Simple LPC I/O|Application Note ; 简单的LPC I / O |应用说明
| 型号： | IT8761E |
| 厂家： | 
ETC |
| 描述： | Simple LPC I/O|Application Note
|
| 文件： | 总1页 (文件大小：28K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
Integrated Technology Express, Inc.
Application Note of IT8761F for
Power On Strapping Circuit
July 1, 1999
Ø Power on strapping circuit needs extra attention when a “0”
setting is selected
Description: Due to IT8761 Rev. B power on strapping pins selection, a “0”
setting may not be strapped in correctly.
Cause:
IT8761 chooses TXD1 and RTS1# pins for power on strapping
setting, since these two pin also connect to 1488/1489 type line
driver and some of the line driver internally have +12V pull up
with a 11K ohm resistor, this will cause the “0” setting not
correctly strapped.
Suggestion: (1) Choose a small enough value pull down resistor to make the
strapping line voltage below 0.5V when system is reset. A
suggested resistor value is 680 ohm.
(2) Implement a redundant gate between IT8671 and line driver
to isolate the interfere of the internal pull up of 1488/89 line
driver as following circuit.
TXD1/RTS1#
1
2
IT8761
1488/89
7407
4.7K
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ITTM-AN-99007, July. 1
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