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CHAPTER 17 USB FUNCTION
■ CONT3
The CONT3 register is used to enable USB transfer at each end point. The address of the
CONT3 register is 0006_0026
Figure 17.2-17 shows the CONT3 register.
Address:0006-0026
H
Table 17.2-10 lists the bits of the CONT3 register and their functions.
Table 17.2-10 Bits of the CONT3 Register
Bit name
BFOK0o
BFOK0i
BFOKn
(n: 1 to 3)
If the ACK0o or ACK0i bit of the ST1 register is set for an end point, the BFOK bit corresponding
to the end point cannot be set. However, even if the NACK0o or NACK0i bit of the ST1 register is
set for an end point, the BFOK bit corresponding to the end point can be set. When device
initialization is completed (when the CFEND bit of the ST3 register is set) or the INIn bit of the
CONT2 register is set, the BFOK bits are set to values as follows:
•
End point for IN transfer: BFOK = 0
•
End point for OUT transfer: BFOK = 1
All bits of CONT3 is enabled by writing 1 only.
After 1 is set to CONT3, and if the FIFO is set to BUBY, set FIFOBUSY bit of CONT4 and
DFIFOBUSY bit of CONT5 to 0.
Writing 1 to the BFOK1 and BFOK2 bits (for double-buffer end points) switches the side of the
double buffer. At the same time, the side of the CONT3 registers is switched accordingly. The
side of the CONT3 register currently available for reading and writing by an application program
corresponds to the side of the FIFO registers currently available for reading and writing. An
application program can access only one side of registers and cannot access the other side of the
registers.
Each BFOK bit is reset when ACK transfer occurs at the corresponding end point.
398
.
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Figure 17.2-17 CONT3 Register
15
14
13
12
11
10
Polarity
ActiveHigh
ActiveHigh
ActiveHigh
9
8
7
6
5
4
B
F
O
K
3
R/W R/W R/W R/W R/W
Function
Writing 1 to this bit enables USB transfer on the
OUT side of end point 0.
Writing 1 to this bit enables USB transfer on the IN
side of end point 0.
Writing 1 to the BFOKn bit enables USB transfer at
end point n.
3
2
1
0
B
B
B
B
F
F
F
F
O
O
O
O
XXXXXXXXXXX00000
K
K
K
K
2
1
0
0
i
o
Initial value
B
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