Oki JOB60851 user manual Data Rates, Device Class Specifications, Maximum Payload Sizes

Chapter 4 Software Development

4-1-8. Data Rates

The USB supports two data rates: 12 Mb/s and 1.5 Mb/s. Table 4.1.4 lists the maximum payload sizes for each combination of data flow type and data rate.

Table 4.1.4. Maximum Payload Sizes

Transfer Types	MAX Payload Size
	12 Mbps	1.5 Mbps
Control	8/16/32/64	8
Isochronous	1023 or less	N/A
Interrupt	64 or less	8 or less
Bulk	8/16/32/64	N/A

A hub determines the data rates supported by an attached function by examining the latter's Non Return to Zero Invert (NRZI) data signal lines (D+ and D-). A device supporting the high speed pulls up the D+ line to the 3.3-volt power supply voltage with a 1.5-kΩresistor; one supporting the low speed does the same with the D- line.

The ML60851C USB controller operates exclusively at 12 Mb/s, so the JOB60851 board includes only the D+ pull-up resistor.

4-1-9. Device Class Specifications

The Universal Serial Bus Device Class Specifications complement the core specifications by further standardizing USB devices for major interfaces and specific applications devices using those interfaces.

Some interface specifications standardize the communications pathways that the USB hardware provides for a specific purpose--the exchange of isochronous audio or image data, for example. Others standardize USB specifications for devices combining multiple interfaces.

Table 4.1.5 lists some of the USB Device Class Specifications currently available. For further details, refer to the following URL.

Table 4.1.5. USB Device Class Specifications

Device Class	Applicable Equipment
Human interface devices (HIDs)	Mice, keyboards, joysticks, etc.
Printers	Printers
Audio devices	Speakers, microphones, etc.
Communications devices	Modems, ISDN terminal adapters, etc.
Mass storage devices	Fl oppy disk drives, SCSI equipment, ATAPI equipment, etc.
Image devices	Digital cameras, scanners, low-rate video, etc.

There is also a standard for downloading programs to devices.

http://www.usb.org/developers/devclass.html

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