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Section 26 USB 2.0 Host/Function Module
R01UH0134EJ0400 Rev. 4.00 Page 1535 of 2108
Sep 24, 2014
SH7262 Group, SH7264 Group
(3) Interval Counter
The isochronous interval can be set using the IITV bits in PIPEPERI. The interval counter enables
the functions shown in table 26.29 when the function controller function is selected. When the
host controller function is selected, this module generates the token issuance timing. When the
host controller function is selected, the interval counter operation is the same as the interrupt
transfer operation.
Table 26.29 Functions of the Interval Counter when the Function Controller Function is
Selected
Transfer
Direction Function Conditions for Detection
IN IN buffer flush function When an IN token cannot be normally received in the
interval frame during an isochronous IN transfer
OUT Notifies that a token not
being received
When an OUT token cannot be normally received in
the interval frame during an isochronous OUT transfer
The interval count is carried out when an SOF is received or for interpolated SOFs, so the
isochronisms can be maintained even if an SOF is damaged. The frame interval that can be set is
the 2
IITV
frame or 2
IITV
frames.
(a) Interval Counter Initialization when the Function Controller Function is Selected
This module initializes the interval counter under the following conditions.
Power-on reset
The IITV bit is initialized.
Buffer memory initialization using the ACLRM bit
The IITV bits are not initialized but the count value is.
USB bus reset
After the interval counter has been initialized, the counter is started under the following conditions
1 or 2 when a packet has been transferred normally.
1. An SOF is received following transmission of data in response to an IN token, in the PID =
BUF state.
2. An SOF is received after data following an OUT token is received in the PID = BUF state.