
26 USB
S1C38000 TECHNICAL MANUAL
EPSON
251
bit 0
USB String Enable
When set, this bit allows the default Vendor and Product String Descriptors to be
returned to the host. When this bit is cleared, the string index values in the Device
Descriptor are set to zero.
bits 7–0
Maximum Current Bits [7:0]
The amount of current drawn by the peripheral from the USB port in increments of 2
mA. The S1C38000 reports this value to the USB host controller in the configuration
descriptor. The default is 500 mA (FAh
× 2 mA).
These bits have no effect in Isochronous mode.
bit 7
EP4 Data Toggle Bit
Contains the value of the Data Toggle bit to be sent in response to the next IN token to
endpoint 4 from the USB host.
Note: When a write is made to this bit, the value cannot be read back before a minimum of 12
USBCLK.
bit 6
EP3 Data Toggle Bit
Contains the value of the Data Toggle bit expected in the next DATA packet to endpoint
3 from the USB host.
bit 5
EP2 Data Toggle Bit
Contains the value of the Data Toggle bit to be sent in response to the next IN token to
endpoint 2 from the USB host.
bit 4
EP1 Data Toggle Bit
Contains the value of the Data Toggle bit expected in the next DATA packet to endpoint
1 from the USB host.
bit 3
EP4 Data Toggle Mode
When set, this bit resets the Data Toggle bit to zero at the end of a USB transfer from
EP4. When cleared, the Data Toggle bit strictly toggles.
Note: When the Data Toggle mode is set to 0, the EP4 toggles every EP4 transfer if the transfer
size matches the maximum transfer size for EP4. If the transfer size is less than the
maximum packet size, then the EP4 Data Toggle bit is set to 0.
USB Control
USB[74h], Index[08h] Default = 0000 0001h
Read/Write
n/a
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
n/a
USB
String
Enable
15
14
13
12
11
10
98
76543210
Maximum Power Consumption
USB[74h], Index[09h] Default = 0000 00FAh
Read/Write
n/a
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
n/a
Maximum Current
15
14
13
12
11
10
98
76543210
Packet Control
USB[74h], Index[0Ah] Default = 0000 0000h
Read/Write
n/a
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
n/a
EP4 Data
Toggle
EP3 Data
Toggle
EP2 Data
Toggle
EP1 Data
Toggle
EP4 Data
Toggle
Mode
EP3 Data
Toggle
Mode
n/a
EP1 Data
Toggle
Mode
15
14
13
12
11
10
98
76543210