transmitter using firmware or additional hardware. • Configurable clock output for driving an external CPU or microcontroller. 326 Using Special-function USB Controllers + 3.3V to +5.5V SUPPLY О 20 UART AND CBUS SUPPLY RESET +3.3V OUT USB INTERFACE OPTIONAL OSCILLATOR I 9 I 7 I 6 I 5 28 27 8 24 26 2 I 25 VCC TXD VCC 1 0 RXD RESET# 3V30UT RTS# CTS# USBDM DTR# USBDP DSR# DCD# 0SC0 R 1 # OSC 1 NC NC CBO TEST CB 1 CB2 GND CB3 GND CB4 GND AGND J____ 5 3 1 I 2 9 I 0 6 23 22 I 3 I 4 I 2 ASYNCHRONOUS SERIAL DATA RS-232 STATUS AND CONTROL CONFIGURABLE CBUS FT232R SSOP PINOUT USB UART Figure 15-1: The FT232R converts between USB and asynchronous serial data. The chip can obtain its power from the VBUS line in the USB cable or from an external supply that connects to the VCC pin. The 3V3OUT pin is a +3.3V output. VCCIO is an input whose voltage determines the logic levels on the UART and CBUS pins. The pin can connect to VCC, 3V3OUT, or an external supply. The chip doesn’t require an external oscillator. To convert the asynchronous serial interface to RS-232, use a Maxim MAX232 or similar interface chip. To convert to RS-485, use an SN75176B or similar RS-485 transceiver. 327 Chapter 15 + 3.3V to +5.5V SUPPLY Q UART AND CBUS SUPPLY RESET I 7 USB INTERFACE Ц 24 28 OPTIONAL OSCILLATOR U— 26 7 1 8 2 I 25 vcc DO VCCI 0 D 1 RESET# D2 3V30UT D3 D4 USBDM D5 USBDP D6 D7 NC NC RD# WR# OSCO OSCI TEST RXF# GND TXE# GND GND PWREN# AGND FT245R SSOP PINOUT I 5 3 1 I 2 9 10 6 I 3 14 I 2 PARALLEL DATA BUS READ FROM THE USB FIFO WRITE TO THE USB FIFO DATA AVAILABLE TO READ FROM THE FIFO OK TO WRITE DATA TO THE FIFO GOES HIGH IF IN USB SUSPEND STATE Figure 15-2: The FT245R converts between USB and parallel data. Parallel Interface FT245R Figure 15-2 shows the pin functions for the FT245R USB FIFO. The USB interface and power options are the same as for the FT232R. But instead of an asynchronous serial port, the chip has an 8-bit, bidirectional parallel data bus prom-electric.ru