Copyright © 2015 Future Technology Devices International Limited

9

FT234XD USB TO BASIC UART IC

Version 1.2

Document No.: FT_000753 Clearance No.: FTDI#324

3.2 CBUS Signal Options

The following options can be configured on the CBUS0 I/O pin. These options can be configured in the

internal MTP memory using the software utility FT_PROG which can be downloaded from the FTDI Utilities

(www.ftdichip.com). The default configuration is described in Section 8.

CBUS Signal

Option

CBUS Pin

Description

TRI-STATE

CBUS0

IO Pad is tri-stated

DRIVE 1

CBUS0

Output a constant 1

DRIVE 0

CBUS0

Output a constant 0

TXDEN

CBUS0

Enable transmit data for RS485

PWREN#

CBUS0

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.

TXLED#

CBUS0

Transmit data LED drive – pulses low when transmitting

data via USB. See Section 7.5 for more details.

RXLED#

CBUS0

Receive data LED drive – pulses low when receiving data

via USB. See Section 7.5 for more details.

TX&RXLED#

CBUS0

LED drive – pulses low when transmitting or receiving

data via USB. See Section 7.5 for more details.

SLEEP#

CBUS0

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.

CLK24MHz

CBUS0

24 MHz Clock output.*

CLK12MHz

CBUS0

12 MHz Clock output.*

CLK6MHz

CBUS0

6 MHz Clock output.*

GPIO

CBUS0

CBUS bit bang mode option. Allows the CBUS pin to be

used as general purpose I/O. Configured in the internal

MTP

available from FTDI website (www.ftdichip.com) describes

in more detail how to use CBUS bit bang mode.

BCD Charger

CBUS0

Battery Charging Detection indicates when the device is

connected to a dedicated battery charger host. Active

high output.

BCD Charger#

CBUS0

Inverse of BCD Charger

BitBang_WR#

CBUS0

Synchronous and asynchronous bit bang mode WR#

strobe output.

BitBang_RD#

CBUS0

Synchronous and asynchronous bit bang mode RD#

strobe output.

VBUS Sense

CBUS0

Input to detect when VBUS is present.

Time Stamp

CBUS0

Toggle signal which changes state each time a USB