SH7670 Datasheet, PDF (819/1292 Pages) Renesas Technology Corp – 32-Bit RISC Microcomputer SuperHTM RISC engine Family / SH7670 Series

Section 17 USB 2.0 Host/Function Module (USB)
(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 µs, high-speed: 3 µs) 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).
Rev. 1.00 Nov. 14, 2007 Page 793 of 1262
REJ09B0437-0100