参数资料
型号: FT232RQ-REEL
厂商: FTDI, Future Technology Devices International Ltd
文件页数: 21/43页
文件大小: 0K
描述: IC USB FS SERIAL UART 32-QFN
产品培训模块: USB Introduction
USB-UART Interface Solutions
标准包装: 1
系列: USBmadeEZ-UART
特点: USB 至 UART
通道数: 1,UART
FIFO's: 256 字节
规程: RS232,RS422,RS485
电源电压: 3.3 V ~ 5.25 V
带自动流量控制功能:
带调制解调器控制功能:
带CMOS:
安装类型: 表面贴装
封装/外壳: 32-VFQFN 裸露焊盘
供应商设备封装: 32-QFN 裸露焊盘(5x5)
包装: 标准包装
产品目录页面: 634 (CN2011-ZH PDF)
配用: 768-1023-ND - MOD USB RS232 DEV/EVAL FT232RL
768-1022-ND - MOD USB UART MINI B DEV FT232R
768-1021-ND - MOD USB UART MINI DEV FT232R
768-1019-ND - MOD USB UART DEV FT232R
其它名称: 768-1008-6
Copyright 2010 Future Technology Devices International Limited
28
Document No.: FT_000053
FT232R USB UART IC Datasheet Version 2.10
Clearance No.: FTDI# 38
7.2 USB to RS485 Coverter
FT232R
GND
100nF
VCC
USBDM
USBDP
VCCIO
NC
RESET#
NC
OSCI
OSCO
3V3OUT
A
G
N
D
G
N
D
G
N
D
G
N
D
T
E
S
T
TXD
RXD
RTS#
CTS#
DTR#
DSR#
DCD#
RI#
CBUS0
CBUS1
CBUS2
CBUS3
CBUS4
1
2
3
4
GND
SHIELD
GND
100nF
4.7uF +
5
10nF +
Ferrite Bead
Vcc
TXD
RXD
GND
DB9M
SHIELD
10
TXDEN
GPO
PWREN#
GPIO0
GPIO1
VCCIO
10K
RS485 LEVEL
CONVERTER
Vcc
SP481
5
1
2
3
4
Link
120R
7
6
Figure 7.2 Application Example Showing USB to RS485 Converter
An example of using the FT232R as a USB to RS485 converter is shown in Figure 7.2. In this application,
a TTL to RS485 level converter IC is used on the serial UART interface of the FT232R to convert the TTL
levels of the FT232R to RS485 levels.
This example uses the Sipex SP481 device. Equivalent devices are available from Maxim and Analogue
Devices. The SP481 is a RS485 device in a compact 8 pin SOP package. It has separate enables on both
the transmitter and receiver. With RS485, the transmitter is only enabled when a character is being
transmitted from the UART. The TXDEN signal CBUS pin option on the FT232R is provided for exactly this
purpose and so the transmitter enable is wired to CBUS2 which has been configured as TXDEN. Similarly,
CBUS3 has been configured as PWREN#. This signal is used to control the SP481s receiver enable. The
receiver enable is active low, so it is wired to the PWREN# pin to disable the receiver when in USB
suspend mode. CBUS2 = TXDEN and CBUS3 = PWREN# are the default device configurations of the
FT232R pins.
RS485 is a multi-drop network; so many devices can communicate with each other over a two wire cable
interface. The RS485 cable requires to be terminated at each end of the cable. A link (which provides the
120 termination) allows the cable to be terminated if the SP481 is physically positioned at either end of
the cable.
In this example the data transmitted by the FT232R is also present on the receive path of the SP481.This
is a common feature of RS485 and requires the application software to remove the transmitted data from
the received data stream. With the FT232R it is possible to do this entirely in hardware by modifying the
example shown in Figure 7.2 by logically ORing the FT232R TXDEN and the SP481 receiver output and
connecting the output of the OR gate to the RXD of the FT232R.
Note that the TXDEN is activated 1 bit period before the start bit. TXDEN is deactivated at the same time
as the stop bit. This is not configurable.
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