FT4232H QUAD HIGH SPEED USB TO MULTIPURPOSE UART/MPSSE IC
Datasheet
Version 2.4
Document No.: FT_000060 Clearance No.: FTDI#78
4.4.1
MPSSE Adaptive Clocking
Adaptive clocking is a new MPSSE feature added to the FT24232H MPSSE engine.
The mode is effectively handshaking the CLK signal with a return clock RTCK. This is a technique used by
ARM processors.
The FT4232H will assert the CLK line and wait for the RTCK to be returned from the target device to
GPIOL3 line before changing the TDO (data out line).
TDO
TCK
GPIOL3
RTCK
ARM CPU
FT4232H
Figure 4.5 Adaptive Clocking Interconnect
TDO changes on falling
edge of TCK
TDO
TCK
RTCK
Figure 4.6: Adaptive Clocking waveform
Adaptive clocking is not enabled by default.
See: AN108 - Command Processor For MPSSE and MCU Host Bus Emulation Modes
Copyright © Future Technology Devices International Limited
27
FTDI [ FUTURE TECHNOLOGY DEVICES INTERNATIONAL LTD. ]
