NXP Semiconductors LPC24XX UM10237 - Manual (Page 366)

UM10237_4 © NXP B.V. 2009. All rights reserved.
User manual Rev. 04 — 26 August 2009 366 of 792
NXP Semiconductors
UM10237
Chapter 13: LPC24XX USB device controller
11.4 Read Current Frame Number (Command: 0xF5, Data: read 1 or 2
bytes)
Returns the frame number of the last successfully received SOF. The frame number is
eleven bits wide. The frame number returns least significant byte first. In case the user is
only interested in the lower 8 bits of the frame number, only the first byte needs to be read.
• In case no SOF was received by the device at the beginning of a frame, the frame
number returned is that of the last successfully received SOF.
• In case the SOF frame number contained a CRC error, the frame number returned will
be the corrupted frame number as received by the device.
11.5 Read Test Register (Command: 0xFD, Data: read 2 bytes)
The test register is 16 bits wide. It returns the value of 0xA50F if the USB clocks (usbclk
and AHB slave clock) are running.
11.6 Set Device Status (Command: 0xFE, Data: write 1 byte)
The Set Device Status command sets bits in the Device Status Register.
Table 351. Set Device Status Register bit description
Bit Symbol Value Description Reset
value
0 CON The Connect bit indicates the current connect status of the
device. It controls the CONNECT output pin, used for
SoftConnect. Reading the connect bit returns the current connect
status. This bit is cleared by hardware when the V
BUS
status input
is LOW for more than 3 ms. The 3 ms delay filters out temporary
dips in the V
BUS
voltage.
0
0 Writing a 0 will make the CONNECT pin go HIGH.
1 Writing a 1 will make the CONNECT pin go LOW..
1 CON_CH Connect Change. 0
0 This bit is cleared when read.
1 This bit is set when the device’s pull-up resistor is disconnected
because V
BUS
disappeared. The DEV_STAT interrupt is
generated when this bit is 1.
2 SUS Suspend: The Suspend bit represents the current suspend state.
When the device is suspended (SUS = 1) and the CPU writes a 0
into it, the device will generate a remote wakeup. This will only
happen when the device is connected (CON = 1). When the
device is not connected or not suspended, writing a 0 has no
effect. Writing a 1 to this bit has no effect. 0
0 This bit is reset to 0 on any activity.
1 This bit is set to 1 when the device hasn’t seen any activity on its
upstream port for more than 3 ms.