m5m51016btp Renesas Electronics Corporation., m5m51016btp Datasheet - Page 137

• Manufacturer Part Number: m5m51016btp
• Description: Renesas 16-bit Single-chip Microcomputer M16c Family / M16c/20 Series
• Manufacturer: Renesas Electronics Corporation.

M30245 Group
Rev.2.00 Oct 16, 2006
REJ09B0340-0200
Figure 2.8.1. Frame image
Isochronous trasnfer
Bulk trasnfer
Interrupt trasnfer
(2) Communication Protocol
Host CPU has the initiative for the entire USB communication. Even when data are transmitted to the
host from the device, the host gives the right of use to the device before data are transmitted. The
host, in order to process multiple transfers simultaneously, schedules each transfer in packet unit
within a frame of 1ms interval. The frames image is shown below:
This transfer is used to notify the host of aperiodic and low-frequency data from the device. For
example, they include the notification of out of paper in printer and data concerning devices such as
the mouse and the keyboard.
This transfer is used for continuous and periodic communication. Once the communication path is
established, a transfer rate is guaranteed with a limited delay. The maximum size of transfer data is
specified by the endpoint, which is read by the host as the configuration data of the device. Based on
this data, transfer within the frame is scheduled and the bus time required for transfer of the maxi-
mum size of data is secured with preference. Although the band width and the transfer rate of data
transfer are guaranteed, retransmission is not executed even if an error exists in the transfer. This is
used for streaming data such as animation and audio data which requires real time.
A packet is the unit in which the host CPU or the device secures a bus. In the USB, data are transmit-
ted/received in the packet unit.
A packet is a group of bit data strings (fields), which starts with the SOP (Start-of-Packet) as a part of
the SYNC (synchronous data) field. This is followed by the PID field which identifies a packet type
and, then, each data field of a frame number/ address/ data field, etc., finally ending with EOP (End-
of-Packet) which indicates the end of a packet. The packet types and formats are shown below:
Interrupt Transfer
Isochronous Transfer
Packet
SOF Audiomouse
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1ms
printer/scanner
SOF
Audio
1ms
printer/scanner
SOF Audio
mouse
1ms
printer/scanner
2. USB function