S2R72V27B08 查看數據表（PDF） - Seiko Epson Corp

零件编号

产品描述 (功能)

生产厂家

S2R72V27B08

Supports HS (480 Mbps), FS (12 Mbps), and LS (1.5 Mbps) transfer

Seiko Epson Corp 

4. Explanation of Functions

4.6.2.2

FIFO

The LSI ports include 4.5 kB of FIFO for use with USB data transfers. This

forms the data transfer route with USB. The FIFO capacity of each endpoint

can be assigned as desired by the software. For example, performance can be

improved by assigning a sufficient size FIFO area to the endpoints for bulk

transfers.

4.6.3

Data Flow

Endpoints are assigned to USB FIFO areas on a one-to-one basis, and responses are

returned to USB transactions automatically, depending on effective USB FIFO free

capacity (for OUT transfers) or effective data quantity (for IN transfers). This means the

software does not need to be directly involved in individual transactions, allowing USB

data transfers to be controlled as data flows at the USB FIFO.

CPU

USB FIFO

Endpoint

USB Host

Write

Read

FIFO_Empty

Write

Data quantity <

MaxPktSize

IN token

NAK handshake

IN transaction

(NAK response)

FIFO_Full

FIFO_Empty

Write

FIFO_Full

Empty

Data

Data quantity >=

MaxPktSize

Transfer sent

Data quantity <

MaxPktSize

Data quantity >=

MaxPktSize

IN token

DATA packet

ACK handshake

IN token

NAK handshake

IN token

DATA packet

ACK handshake

IN transaction

(Data reply)

IN transaction

(NAK response)

IN transaction

(Data reply)

Fig. 4.4 Typical data flow (with FIFO assigned for MaxPktSize and IN transfer)

8

EPSON

S2R72V27 Data Sheet (Rev. 1.00)

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