28 USB FUNCTION CONTROLLER (USB)
S1C33L26 TECHNICAL MANUAL
Seiko Epson Corporation
28-41
In every transaction, the DescAdrs_H, L register is incremented as many as the number of data that
were sent, while the DescSize_H, L register is decremented as many as the number of data that were
sent.
When the data transmission ends after sending as many data as specified in the DescSize_H, L or when
a transaction other than the IN transaction is done, the Descriptor reply function ends, the ReplyDe-
scriptor bit is set to 0 (to be cleared) and the IN_TranACK bit of the EP0IntStat register is set to 1.
Refer to the section describing operations, for details.
EP0ControlIN (EP0 Control IN)
Register name Address
Bit
Name
Setting
Init. R/W
Remarks
EP0ControlIN
(EP0 control
IN)
0x300c3a
(8 bits)
D7
–
–
–
–
0 when being read.
D6
EnShortPkt
1 Enable short packet
0 Do nothing
0
R/W
D5
–
–
–
–
0 when being read.
D4
ToggleStat
Toggle sequence bit
0
R
D3
ToggleSet
1 Set toggle sequence bit
0 Do nothing
0
R/W
D2
ToggleClr
1 Clear toggle sequence bit 0 Do nothing
0
R/W
D1
ForceNAK
1 Force NAK
0 Do nothing
0
R/W
D0
ForceSTALL
1 Force STALL
0 Do nothing
0
R/W
This register sets the operations related to the IN transaction of the endpoint EP0 and displays their status.
D7
Reserved
D6
EnShortPkt
Setting this bit to 1 enables to send the data within the FIFO that is less than the quantity specified for
the MaxPacketSize, as a short packet for the IN transaction of the endpoint EP0. When the IN transac-
tion that transmitted short packets completes, this bit is automatically set to 0 (to be cleared). When a
packet of the max packet size is transmitted, this bit is not cleared.
If this bit is set to 1 when the FIFO has no data, a zero-length packet can be transmitted for the IN token
from the host. If the data is written into the FIFO that is in the transmission process with the packet to
which this bit is set, that data may be included in transmission. Therefore, do not write into the FIFO
until the packet transmission completes and this bit is cleared.
D5
Reserved
D4
ToggleStat
Shows the status of the toggle sequence bit in the IN transaction of the endpoint EP0.
D3
ToggleSet
Sets the toggle sequence bit in the IN transaction of the endpoint EP0, to 1.
D2
ToggleClr
Sets the toggle sequence bit in the IN transaction of the endpoint EP0, to 0 (clear).
D1
ForceNAK
If this bit is set to 1, the NAK response is done for the IN transaction of the endpoint EP0, regardless of
the FIFO data quantity.
When the RcvEP0SETUP bit of the MainIntStat register is set to 1 after completion of the setup stage,
this bit is set to 1, and this bit cannot be set to 0 (to be cleared) as long as the RcvEP0SETUP bit is 1.
When the IN transaction that transmitted short packets completes, this bit is set to 1.
When a transaction has been being done for a certain period of time, the setting of this bit will be en-
abled from the next transaction.
D0
ForceSTALL
If this bit is set to 1, the STALL response is done for the IN transaction of the endpoint EP0. This bit
has a priority over the setting of the ForceNAK bit.
When the RcvEP0SETUP bit of the MainIntStat register is set to 1 after completion of the setup stage,
this bit is set to 0 (to be cleared), and this bit cannot be set to 1 as long as the RcvEP0SETUP bit is 1.
When a transaction has been being done for a certain period of time, the setting of this bit will be en-
abled from the next transaction.