Document No.: FT_000053
FT232R USB UART IC Datasheet Version 2.07
Clearance No.: FTDI# 38
3.5 CBUS Signal Options
The following options can be configured on the CBUS I/O pins. CBUS signal options are common to both
package versions of the FT232R. These options can be configured in the internal EEPROM using the
software utility FT_PPROG or MPROG, which can be downloaded from the FTDI Utilities
(www.ftdichip.com). The default configuration is described in Section 8.
CBUS
Signal
Option
Available On CBUS Pin
Description
TXDEN
CBUS0, CBUS1, CBUS2, CBUS3, CBUS4
Enable transmit data for RS485
Output is low after the device has been configured by
USB, then high during USB suspend mode. This output can
be used to control power to external logic P-Channel logic
level MOSFET switch. Enable the interface pull-down
option when using the PWREN# in this way.*
PWREN#
CBUS0, CBUS1, CBUS2, CBUS3, CBUS4
Transmit data LED drive – pulses low when transmitting
data via USB. See Section 7.5 for more details.
TXLED#
RXLED#
CBUS0, CBUS1, CBUS2, CBUS3, CBUS4
CBUS0, CBUS1, CBUS2, CBUS3, CBUS4
CBUS0, CBUS1, CBUS2, CBUS3, CBUS4
Receive data LED drive – pulses low when receiving data
via USB. See Section 7.5 for more details.
LED drive – pulses low when transmitting or receiving data
via USB. See Section 7.5 for more details.
TX&RXLED#
Goes low during USB suspend mode. Typically used to
power down an external TTL to RS232 level converter IC
in USB to RS232 converter designs.
SLEEP#
CBUS0, CBUS1, CBUS2, CBUS3, CBUS4
CLK48
CLK24
CLK12
CLK6
CBUS0, CBUS1, CBUS2, CBUS3, CBUS4
CBUS0, CBUS1, CBUS2, CBUS3, CBUS4
CBUS0, CBUS1, CBUS2, CBUS3, CBUS4
CBUS0, CBUS1, CBUS2, CBUS3, CBUS4
48MHz Clock output.**
24 MHz Clock output.**
12 MHz Clock output.**
6 MHz Clock output.**
CBUS bit bang mode option. Allows up to 4 of the CBUS
pins to be used as general purpose I/O. Configured
individually for CBUS0, CBUS1, CBUS2 and CBUS3 in the
internal EEPROM. A separate application note, AN232R-01,
available from FTDI website (www.ftdichip.com) describes
in more detail how to use CBUS bit bang mode.
CBitBangI/O
CBUS0, CBUS1, CBUS2, CBUS3
Synchronous and asynchronous bit bang mode WR#
strobe output.
BitBangWRn
BitBangRDn
CBUS0, CBUS1, CBUS2, CBUS3
CBUS0, CBUS1, CBUS2, CBUS3
Synchronous and asynchronous bit bang mode RD# strobe
output.
Table 3.9 CBUS Configuration Control
* PWREN# must be used with a 10kΩ resistor pull up.
**When in USB suspend mode the outputs clocks are also suspended.
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