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Copyright © 2012 Future Technology Devices International Limited

UMFT240XE

Version 1.0

Document Reference No.: FT_000653

Clearance No.: FTDI#

295

4.3

CBUS Signal Options

The following options can be configured on the CBUS I/O pins. These options are all configured in the

internal MTP ROM using the utility software FT_PROG, which can be downloaded from the

www.ftdichip.com. The default configuration is described in Section 9.

CBUS Signal

Option

Available On CBUS Pin

Description

Tristate

CBUS5, CBUS6

IO Pad is tri-stated

DRIVE_1

CBUS5, CBUS6

Output a constant 1

DRIVE_0

CBUS5, CBUS6

Output a constant 0

PWREN#

CBUS5, CBUS6

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.

NOTE: This function is driven by an open-drain to ground with no

internal pull-up, this is specially designed to aid battery charging

applications. UMFT240XE connects an on-board 47K pull-up on each

CBUS and DBUS signal.

TXLED#

CBUS5, CBUS6

Transmit data LED drive – open drain pulses low when transmitting data

via USB.

RXLED#

CBUS5, CBUS6

Receive data LED drive – open drain pulses low when receiving data via

USB.

TX&RXLED#

CBUS5, CBUS6

LED drive – open drain pulses low when transmitting or receiving data

via USB.

SLEEP#

CBUS5, CBUS6

Goes low during USB suspend mode. Typically used to power down an

external logic to RS232 level converter IC in USB to RS232 converter

designs. Deactivate SLEEP# option for when connected to a dedicated

charger port, this can be selected when configuring the MTP ROM. When

this option is enabled SLEEP# is driven high when FT240X is connected

to a Dedicated Charger Port.

CLK24MHz

CBUS5, CBUS6

24 MHz Clock output.**

CLK12MHz

CBUS5, CBUS6

12 MHz Clock output.**

CLK6MHz

CBUS5, CBUS6

6 MHz Clock output.**

BCD_Charger

CBUS5, CBUS6

Battery Charge Detect indicates when the device is connected to a

dedicated battery charger host. Active high output. NOTE: Requires a

10K pull-down to remove power up toggling.

BCD_Charger#

CBUS5, CBUS6

Active low BCD Charger, driven by an open drain to ground with no

internal pull-up (4.7K on board pull-up present).

BitBang_WR#

CBUS5, CBUS6

Synchronous and asynchronous bit bang mode WR# strobe output.

BitBang_RD#

CBUS5, CBUS6

Synchronous and asynchronous bit bang mode RD# strobe output.

VBUS Sense

CBUS5, CBUS6

Input to detect when VBUS is present.

Time Stamp

CBUS5, CBUS6

Toggle signal which changes state each time a USB SOF is received

Keep_Awake#

CBUS5, CBUS6

Active Low input, prevents the chip from going into suspend.

Table 4.2 – CBUS Signal Options

**When in USB suspend mode the outputs clocks are also suspended.