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APPLICATION
2.4 USB
7532/7536 Group User’s Manual
Fig. 2.4.17 Processing for width of SE0 signal
2.4.5 Notes concerning USB
(1)
Determination of resume interrupt
The occurrence of the resume interrupt cannot be determined directly because there is no corresponding
interrupt request flag when the resume interrupt occurs in the OUT token interrupt processing.
Accordingly, determine the occurrence of the resume interrupt from other interrupt conditions in the
order shown in Figure 2.4.16.
Fig. 2.4.16 Example for determination of resume interrupt
(2)
Clear of suspend request flag
When the request of the suspend interrupt occurs, the suspend request flag is set to “1”. After the
suspend state is fixed, the state of this flag is retained during fixed time (13
μ
s).
The purpose of this is to retain the internal state until the count source to measure the time (3 ms)
until suspend is fixed is updated.
Accordingly, the state might not change even if this flag is cleared to “0” immediately after the
suspend request flag is “1” is determined.
Clear this flag to “0” after the wait of 13
μ
s or 79 machine cycle (f(X
IN
) =6 MHz time) after this flag is “1”.
(3)
Determination of SE0 signal
In 7532/7536 Group, USB reset and EOP can be distinguished according to the width of the SE0 signal.
However, there is the time zone which corresponds any on the dividing line of the time of the width of the
signal.
Moreover, the control in a present state is required because there is a difference in processing by
the state of the device.
Accordingly, select the processing method in software by the state of the device.
Figure 2.4.17 shows processing to the width of the signal according to the situation.
OUT token interrupt
Interrupt source = Token
No Token
Interrupt source = Suspend
Reset/Resume
Execute Resume processing
USBIR2
2
USBIR2
2
Token
Suspend
To Suspend
processing
To SETUP/OUT token
processing
Interrupt source = Reset
Resume
Reset
To Reset
processing
USBIR2
2
Interrupt by Reset occurs if = “1”
G
: Not used here.
Set it to “0” or “1” arbitrary.
Interrupt by the source except token occurs if = “0”
Interrupt by Suspend occurs if = “1”
0
μ
s
Idle state
EOP(RxPID=1)
Signal ignored
0.50
μ
s
2.50
μ
s
2.67
μ
s
D-pin state
TKNE, RSME, RSTE
Token phase state
Data/Handshake
phase state
Suspend state
Signal ignored(FEOPE=1)
1
0
0
0
0
0
0
1
1
1
0/1
Signal ignored(FEOPE=1)
Keep Alive
Keep Alive/Reset(RSTRQ=1)
Reset(RSTRQ=1)
Reset(RSTRQ=1)/Resume(RSTRQ=0)
Reset(RSTRQ=1)
Reset(RSTRQ=1)
EOP(RxPID=1)/Reset(RxPID=0)
Note:
Each active state represents the processing is required in “H” state.
EOP(EOP=1)
EOP(RSTRQ=0)/Reset(RSTRQ=1)