FT220X USB 4-BIT SPI/FT1248 IC Datasheet
Version 1.3
Document No.: FT_000629 Clearance No.: FTDI# 262
3.3 CBUS Signal Options
The following options can be configured on the CBUS I/O pin. CBUS signal options are common to both
package versions of the FT220X. 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 9.
CBUS
Signal
Option
Available On CBUS Pin
Description
TRI-STATE
DRIVE 1
DRIVE 0
CBUS3
CBUS3
CBUS3
IO Pad is tri-stated
Output a constant 1
Output a constant 0
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#
SLEEP#
CBUS3
CBUS3
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
CLK12MHz
CLK6MHz
CBUS3
CBUS3
CBUS3
24 MHz Clock output.*
12 MHz Clock output.*
6 MHz Clock output.*
CBUS bit bang mode option. Allows the CBUS pins to be
used as general purpose I/O. Configured in the internal
MTP memory. A separate application note, AN232R-01,
available from FTDI website (www.ftdichip.com) describes
in more detail how to use CBUS bit bang mode.
GPIO
CBUS3
CBUS3
Battery Charger Detect, indicates when the device is
connected to a dedicated battery charger port. Active high
output.
BCD Charger
BCD
Charger#
CBUS3
CBUS3
Inverse of BCD Charger (open drain)
Synchronous and asynchronous bit bang mode WR#
strobe output.
BitBang_WR#
Synchronous and asynchronous bit bang mode RD# strobe
output.
BitBang_RD#
VBUS Sense
Time Stamp
CBUS3
CBUS3
CBUS3
Input to detect when VBUS is present.
Toggle signal which changes state each time a USB SOF is
received
Prevents the device from entering suspend state when
unplugged.
Keep_Awake#
CBUS3
Table 3.7 CBUS Configuration Control
*When in USB suspend mode the outputs clocks are also suspended.
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