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Application Note
AN_289 FT51A Programming Guide
Version 1.0
Document Reference No.: FT_000962 Clearance No.: FTDI# 483
87
Copyright © 2015 Future Technology Devices International Limited
2.11
USB Full Speed Device Controller
The FT51A contains USB Full Speed device controller based on the
to access the device are shown in Table 2.112.
SFR
Address
Register Name
Description
0xFC
FT122_CMD
Command register.
0xFD
FT122_DATA
Data register.
Table 2.112 USB Full Speed device controller Register Addresses
The device is addressed by writing the command code from Table 2.117 or Table 2.118 into the
FT122_CMD
register and then optionally reading or writing data to the
FT122_DATA
register.
2.11.1
Endpoint Buffer Management
The USB Full Speed device controller has 2 modes of operation for command and memory
management: the default mode (FT120 compatible mode) and the enhanced mode. The buffer
management schemes are different in these two modes. Upon reset the default mode is functional.
The enhanced mode is activated when any of the Set Endpoint Configuration commands (0xB0 to
0xBF) is received.
2.11.1.1
Endpoint Buffer Management in Default Mode
In default mode, the USB Full Speed device controller has 3 bi-directional endpoints (EP0, EP1 and
EP2). EP0 is the control endpoint, with 16 bytes maximum packet size for both control OUT and
control IN transfers. EP1 can be used as either a bulk endpoint or an interrupt endpoint, with 16
bytes maximum packet size for both OUT and IN transfers. Table 2.113 shows the endpoint type
and maximum packet size for EP0 and EP1.
Endpoint
Number
(EP)
Endpoint
Index
(EPI)
Endpoint
Direction
Transfer Type
Max Packet
Size
0
0
1
OUT
IN
Control
Control
16
16
1
2
3
OUT
IN
Bulk/Interrupt
Bulk/Interrupt
16
16
Table 2.113 Endpoint Configuration for EP0 and EP1
EP2 is the primary endpoint. It can be configured for either bulk/interrupt or isochronous transfers.
The maximum packet size allowed for EP2 is configured using the Set Mode command. Table 2.114
shows all four endpoint configuration modes for EP2.