UPSD3422EB40U6 datasheet(159/300 Pages) STMICROELECTRONICS

159 / 300 page

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Product(s)

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Product(s)

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Product(s)

- Obsolete

Product(s)

UPSD3422, UPSD3433, UPSD3434, UPSD3454

USB interface

159/300

Figure 54.

FIFO pairing example (1/2 IN paired and 3/4 OUT paired)

25.3.4

Reading and writing FIFOs

There are a total of ten 64-byte FIFOs. Each of the five Endpoints has two FIFOs, one IN

FIFO for IN transactions and one OUT FIFO for OUT transactions. The FIFOs are

accessible by the CPU through a 64-byte segment in the XDATA space when the VISIBLE

Bit is set (see Table 120 on page 170). If the VISIBLE Bit is not set, the FIFOs are not

accessible by the CPU but are still accessible by the SIE. The base address of the 64-byte

segment is specified by the USB base address high register (see Table 130 on page 175)

and the USB base address low register (see Table 132 on page 175). When the VISIBLE Bit

is set, the FIFO that is accessible in the 64-byte XDATA space segment is the FIFO selected

by the USEL register. The USEL register contains two fields used for selecting the

accessible FIFO. The EP field determines the Endpoint selected and the DIR Bit selects the

IN or OUT FIFO associated with the Endpoint.

25.3.5

Accessing FIFO control registers, UCON, and USIZE

Each of the 10 Endpoint FIFOs has an associated USB endpoint control register (UCON,

0F1H) and a USB FIFO valid size register (USIZE, 0F2H). The USB endpoint select register

(USEL) is not only used to select the Endpoint FIFO that is accessible in the XDATA space,

but also selects the associated Endpoint’s UCON and USIZE registers that are accessible at

SFR addresses 0F1H and 0F2H.

8032

MCU

USB SFRs

Serial

interface

engine

CTRL

XDATA

AI10494b

Endpoint4 IN FIFO

Endpoint3 IN FIFO

Endpoint2 IN FIFO

Endpoint1 IN FIFO

Endpoint0 IN FIFO

Endpoint0 OUT FIFO

Endpoint1 OUT FIFO

Endpoint2 OUT FIFO

FIFO

interface

logic

Endpoint4

Endpoint3

Endpoint2

(not available)

Endpoint2

(not available)

Endpoint1

Endpoint0

Endpoint4

Endpoint3

Endpoint1

Endpoint0

Endpoint1

Endpoint2

Endpoint3

Endpoint0

Endpoint1

Endpoint2

Endpoint3

Endpoint4

(not available)

Endpoint4

(not available)

Endpoint3 OUT FIFO

Endpoint4 OUT FIFO

Obsolete

Product(s)

- Obsolete

Product(s)

UPSD3422EB40U6 Datasheet(PDF) 159 Page - STMicroelectronics

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