Toshiba TLCS-900/H1 Series Manual page 275

(c) Issuance of NULL packet
If transmitting NULL packet, by input L pulse from EPx_EOPB signal, data of 0
length is set to FIFO, and NULL packet can be transferred to IN token.
But if NULL data is set to FIFO, it is valid only in the case where SET signal is L
level condition (where FIFO is empty). If it answers to receiving IN token by using
NULL packet in a certain period, it is answered by keeping EPx_EOPB signal to L
level.
However, if mode is dual packet mode, EPx_DATASET signal assert L level for
showing space of data. Therefore, data condition (whether either has data or not)
cannot be confirmed externally.
Note: NULL packet can also be set by accessing EOP register.
Example:
DATASET_A
DATASET_B
EPx_EOPB
NULL
A
(2) Interrupt control
Interrupt signal is prepared. This function uses adept system.
For detail refer to 3.10.2 900/H1 CPU I/F.
NULL packet
completion of
transmitting
Neglect NULL NULL
B A
92CH21-273
NULL NULL
B A
TMP92CH21
2009-06-19