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CHAPTER 30 USB Mini-host
30.5.1
Device Connection
Operation of the external USB device connection detection.
■ Setting of Mini-host function
The HCNT0:HOST bit must be set to "1" to turn the USB function as a host.
■ Disconnection status, connection status of an external USB device
When the external USB device is disconnected, both Mini-host pins, D+ and D-, are "L" by the
pull-down resistor. HSTATE:CSTAT bit is therefore set to "0", and the TMODE bit is undefined.
The HSTATE:CSTAT bit becomes "1" when the external USB device is connected, i.e., when a
polarity change on the D+ and D- indicates the presence of a device.
■ Connection detection of an external USB device
To detect the connection of the external USB device, HCNT0:CNNIRE bit must be set to "1".
Thus, when HIRQ:CNNIRQ bit becomes "1" a device connection interrupt is generated. Clearing
this bit, clears the interrupt. To detect the connection of the external USB device not through
interrupt but through polling, a program must check that the HCNT0:CNNIRE bit is set to "0" and
the HIRQ:CNNIRQ bit is set to "1".
■ Acquiring transfer speed of destination USB device and selecting the clock
HSTATE:TMODE bit holds the information regarding the transfer speed of a USB device.
When a destination device is a Full Speed device then TMODE = "1" .
Note:
TMODE = "0" has no effect on speed since Low Speed mode is not supported by this device.
Figure 30.5-1
Terminal D+ for Mini-HOST
Terminal D- for Mini-HOST
CSTAT bit of HSTATE
TMODE bit of HSTATE
CNNIRQ of HIRQ bit
HOST bit of HCNT
Note:
The HSTATE:CSTAT bit is set to "1" within 2.5 ms after the external USB device connection.
The HSTATE:TMODE and CSTAT bits are updated regardless of the setting of the
796
C onnection detection timing example of the USB device speed
LIN device connection
Indeterminate
2.5µs
"0"
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