Universal Serial Bus
81
Specifications in this manual are tentative and subject to change
Rev. E
MITSUBISHI MICROCOMPUTERS
M30245 Group
SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER
USB Control Register
The USB Control Register, shown in Figure 1.45, is used to control the USB FCU. This register is not
reset by USB reset signaling. After the USB is enabled (USBC7 set to “1”), a minimum delay of 250ns
(three 12 MHz clock periods) is needed before performing any other USB register read/write operations.
USBC5 (USB Clock Enable):
The USB clock enable bit is used to enable or disable the USB clock (fUSB). This clock is derived from
the Frequency Synthesizer and is required for USB operation.
USBC6 (SOF port select):
The SOF port select bit enables or disables outputting a SOF signal on the P92/SOF pin. When this bit is
set to "1", an active low pulse is output each time a start of frame packet is detected on the USB. The
output pulse width is 166ns (two 12MHz USB clock cycles).
USBC7 (USB Enable):
The USB enable bit is used to enable or disable the USB block. Make sure the USB clock is enabled
before setting this bit to "1".
Figure 1.45. USB Control register (USBC)
Figure 1.46. USB Function Address register (USBA)
USB Function Address Register
The USB Function Address Register, shown in Figure 1.46, maintains the 7-bit USB address assigned by
the host. The USB FCU uses this register value to decode USB token packet addresses. At reset, when the
device is not yet configured, the value is 0016. (For the procedures on how to update this register, refer to
Application Notes USB Consecutive Set Address)
Bit Symbol
Bit Name
Function
R W
Reserved
USBC5
USBC6
USBC7
O O
Symbol
USBC
Address
000C
16
When reset
00
16
USB Control register
b7
b5
b6
b4
b3
b2
b1
b0
Must always be set to "0"
0 : Disable
1 : Enable
0 : Disable (Note 1)
1 : Enable
0 : Disable (Note 2)
1 : Enable
O O
USB clock enable bit
USB SOF port select bit
USB enable bit
O O
Note 1: P9
2 is used as GPI/O pin.
Note 2: All USB internal registers are held at their default values.
0
Bit Symbol
Bit Name
Function
R W
Must always be "0"
O O
Symbol
USBA
Address
0280
16
When reset
0000
16
USB Function Address register
b7
(b15)
(b8)
b0
FUNAD6-0
b7
b0
0 0 000 000
Function address
7-bit programmable
function address
O O
Reserved
0