NXP Semiconductors LPC1768 - Read Test Register (Command: 0 Xfd, Data: Read 2 Bytes); Set Device Status (Command: 0 Xfe, Data: Write 1 Byte)

UM10360 All information provided in this document is subject to legal disclaimers. © NXP B.V. 2013. All rights reserved.
User manual Rev. 3 — 19 December 2013 248 of 841
NXP Semiconductors
UM10360
Chapter 11: LPC176x/5x USB device controller
• 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.
11.12.5 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.
11.12.6 Set Device Status (Command: 0xFE, Data: write 1 byte)
The Set Device Status command sets bits in the Device Status Register.
Table 245. Set Device Status command 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 wake-up. 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.
3 SUS_CH Suspend (SUS) bit change indicator. The SUS bit can toggle because:
• The device goes into the suspended state.
• The device is disconnected.
• The device receives resume signalling on its upstream port.
This bit is cleared when read.
0
0 SUS bit not changed.
1 SUS bit changed. At the same time a DEV_STAT interrupt is generated.