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UM10375
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© NXP B.V. 2011. All rights reserved.
User manual
Rev. 3 — 14 June 2011
150 of 368
NXP Semiconductors
UM10375
Chapter 10: LPC13xx USB device controller
10.10.2.2 USB Command Data register (USBCmdData - 0x4002 0014)
This register contains the data retrieved after executing a SIE command. When the data is
ready to be read, the CD_FULL bit of the USBDevIntSt register is set. USBCmdData is a
read only register.
10.10.3 USB data transfer registers
The registers in this group are used for transferring data between endpoint buffers and
RAM in Slave mode operation. See
Section 10.13 “Functional description”
10.10.3.1 USB Receive Data register (USBRxData - 0x4002 0018)
For an OUT transaction, the CPU reads the endpoint buffer data from this register. Before
reading this register, the RD_EN bit and LOG_ENDPOINT field of the USBCtrl register
should be set appropriately. On reading this register, data from the selected endpoint
buffer is fetched. The data is in little endian format: the first byte received from the USB
bus will be available in the least significant byte of USBRxData. USBRxData is a read only
register.
10.10.3.2 USB Transmit Data register (USBTxData - 0x4002 021C)
For an IN transaction, the CPU writes the endpoint data into this register. Before writing to
this register, the WR_EN bit and LOG_ENDPOINT field of the USBCtrl register should be
set appropriately, and the packet length should be written to the USBTxPlen register. On
writing this register, the data is written to the selected endpoint buffer. The data is in little
endian format: the first byte sent on the USB bus will be the least significant byte of
USBTxData. USBTxData is a write only register.
10.10.3.3 USB Receive Packet Length register (USBRxPLen - 0x4002 0020)
This gives the number of bytes remaining in the RAM for the current packet being
transferred and whether the packet is valid or not. This register will get updated at every
word that gets transferred to the system. The processor can use this register to get the
number of bytes to be transferred. When the number of bytes reaches zero, an end of
packet interrupt is generated.
Table 168. USB Command Data register (USBCmdData - address 0x4002 0014) bit
description
Bit
Symbol
Description
Reset value
7:0
CMD_RDATA
Command Read Data.
0x00
31:8
-
Reserved, user software should not write ones to reserved
bits. The value read from a reserved bit is not defined.
NA
Table 169. USB Receive Data register (USBRxData - address 0x4002 0018) bit description
Bit
Symbol
Description
Reset value
31:0
RX_DATA
Data received.
0x0000 0000
Table 170. USB Transmit Data register (USBTxData - address 0x4002 001C) bit description
Bit
Symbol
Description
Reset value
31:0
TX_DATA
Transmit Data.
0x0000 0000