Figure 18.11 Operation On Receiving An In Token (Ep2-In: Initial Fifo Is Empty) - Renesas H8S/2158 User Manual

USB Host
Send an IN token packet
Receive a NAK
handshake packet
Re-transmission
Send an IN token packet
Receive an IN data
packet (8 bytes)
Receive an ACK
handshake packet
Notes: 1. When an EP2TF interrupt is specified as a USBIB or USBIC interrupt according to the INTSELR0 setting, the corresponding interrupt occurs.
In this case, if a USBIB or USBIC interrupt occurs, interrupt source determination process is not required. (Note that TFFR0 must be
accessed to clear the flags.)
2. When an EP2TS interrupt is specified as a USBIB or USBIC interrupt according to the INTSELR0 setting, the corresponding interrupt occurs.
In this case, if a USBIB or USBIC interrupt occurs, interrupt source determination process is not required. (Note that TSFR0 must be
accessed to clear the flags.)

Figure 18.11 Operation on Receiving an IN Token (EP2-IN: Initial FIFO Is Empty)

USB Function Core
Receive an IN token packet
Send NAK to the host CPU
Send NAK to the slave CPU
Receive an IN token packet
Receive an IN data
packet (8 bytes)
Receive ACK
Send ACK to the slave CPU
Section 18 Universal Serial Bus Interface (USB)
Core Interface
Disable data read
because the EP2 FIFO is
empty
Request an USBID
interrupt (EP2TF) * 1
Write data to the EP2 FIFO
Modify FVSR2 and enable
data transmission
Read data from the EP2
FIFO
Modify FVSR2
Request an USBID
interrupt (EP2TS) * 2
Rev. 3.00 Jan 25, 2006 page 615 of 872
Slave CPU
Initiate the USBID interrupt
processing
Read USBIFR0 and check
if a TF interrupt occurs
or not
Read TFFR0 and check
if an EP2TF interrupt occurs
or not
Read FVSR2 and write data
to EPDR2 for the number
of bytes which can be
written to the EP2 FIFO
Set the EP2TE bit of
PTTER0 to 1
Clear the EP2TF bit of
TFFR0 to 0
Complete the USBID
interrupt processing
Initiate the USBID
interrupt processing
The following procedure is
the same as that when
the initial FIFO is full.
REJ09B0286-0300