SH7670 Datasheet, PDF (818/1292 Pages) Renesas Technology Corp – 32-Bit RISC Microcomputer SuperHTM RISC engine Family / SH7670 Series

Section 17 USB 2.0 Host/Function Module (USB)
(8) Response PID = NAK Function
This module has a function that disables pipe operation (PID response = NAK) at the timing at
which the final data packet of a transaction is received (this module automatically distinguishes
this based on reception of a short packet or the transaction counter) by setting the SHTNAK bit in
PIPECFG to 1.
When a double buffer is being used for the buffer memory, using this function enables reception
of data packets in transfer units. If pipe operation has disabled, the pipe has to be set to the enabled
state again (PID response = BUF) using software.
This function can be used only when bulk transfers are used.
(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.
Rev. 1.00 Nov. 14, 2007 Page 792 of 1262
REJ09B0437-0100