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Section 26 USB 2.0 Host/Function Module
Page 1508 of 2108 R01UH0134EJ0400 Rev. 4.00
Sep 24, 2014
SH7262 Group, SH7264 Group
(9) Auto Transfer MODE
With the pipes for bulk transfer (PIPE1 to PIPE5), when the ATREPM bit in PIPEnCTR is set to
1, a transition is made to auto response mode. During an OUT transfer (DIR = 0), OUT-NAK
mode is entered, and during an IN transfer (DIR = 1), null auto response mode is entered.
(a) OUT-NAK Mode
With the pipes for bulk OUT transfer, NAK is returned in response to an OUT or PING token and
an NRDY interrupt is output when the ATREPM bit is set to 1. To make a transition from normal
mode to OUT-NAK mode, OUT-NAK mode should be specified in the pipe operation disabled
state (response PID = NAK) before enabling pipe operation (response PID = BUF). After pipe
operation has been enabled, OUT-NAK mode becomes valid. However, if an OUT token is
received immediately before pipe operation is disabled, the token data is normally received, and
an ACK is retuned to the host.
To make a transition from OUT-NAK mode to normal mode, OUT-NAK mode should be
canceled in the pipe operation disabled state (response PID = NAK) before enabling pipe
operation (response PID = BUF). In normal mode, reception of OUT data is enabled and an ACK
is returned in response to a PING token if the buffer is ready to receive data.
(b) Null Auto Response Mode
With the pipes for bulk IN transfer, zero-length packets are continuously transmitted when the
ATREPM bit is set to 1.
To make a transition from normal mode to null auto response mode, null auto response mode
should be set in the pipe operation disabled state (response PID = NAK) before enabling pipe
operation (response PID = BUF). After pipe operation has been enabled, null auto response mode
becomes valid. Before setting null auto response mode, INBUFM = 0 should be confirmed
because the mode can be set only when the buffer is empty. If the INBUFM bit is 1, the buffer
should be emptied with the ACLRM bit. While a transition to null auto response mode is being
made, data should not be written from the FIFO port.
To make a transition from null auto response mode to normal mode, pipe operation disabled state
(response PID = NAK) should be retained for the period of zero-length packet transmission (full-
speed: 10 s, high-speed: 3 s) before canceling null auto response mode. In normal mode, data
can be written from the FIFO port; therefore, packet transmission to the host is enabled by
enabling pipe operation (response PID = BUF).