FT120T-R datasheet(16/40 Pages) FTDI

16 / 40 page

Document No.: FT_000646

FT120 USB DEVICE CONTROLLER WITH PARALLEL BUS IC

Datasheet Version 1.2

Clearance No.: FTDI#

291

Bit

Symbol

Reset

Description

11: Mode 3 (ISO-IO Mode)

Table 6-4 Configuration Register (Byte 1)

Bit

Symbol

Reset

Description

3-0

Clock Division Factor

0b’1011

The Clock Division Factor value (CDF) determines the

output clock frequency on the CLKOUT pin. Frequency =

48 MHz / (CDF +1), where CDF ranges 1-12 or the

allowed CLKOUT frequency is 4-24 MHz. Default CLKOUT

is 4 MHz.

When the CDF is programmed to 0b’1111, the CLKOUT

will be turned off. It is recommended to turn off the

CLKOUT if it not used, for power saving (about 3mA).

Note: The programmed value will not be changed by a

bus reset.

5-4

Reserved

0b’00

Reserved, write to 0

SET_TO_ONE

This bit must be set to 1

SOF-only Interrupt

Mode

0: normal operation

1: interrupt will generate on receiving SOF packet only,

regardless of the value of the Interrupt Pin Mode bit in

the DMA configuration register.

Table 6-5 Clock Division Factor Register (Byte 2)

6.2.4 Set DMA

Command

: FBh

Data

: Read/Write 1 byte

Bit

Symbol

Reset

Description

1-0

DMA Burst

0b’00

Set the DMA burst size

00: Single cycle mode

01: 4 cycle burst mode

10: 8 cycle burst mode

11: 16 cycle burst mode

DMA Enable

Enable DMA operation

0: DMA operation is disabled

1: DMA operation is enabled

FT120 will clear this bit upon EOT_n assertion.

DMA Direction

This bit indicates the DMA read or write operation.

0: DMA read. Data read from FT120 OUT buffer to

system memory.

1: DMA write. Data write to FT120 IN buffer from system

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