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UM10316_0
© NXP B.V. 2008. All rights reserved.
User manual
Rev. 00.06 — 17 December 2008
171 of 571
NXP Semiconductors
UM10316
Chapter 13: LPC29xx USB device
9.4.4 USB MaxPacketSize register (USBMaxPSize - 0xE010 C24C)
On reset, the control endpoint is assigned the maximum packet size of 8 bytes. Other
endpoints are assigned 0. Modifying USBMaxPSize will cause the endpoint buffer
addresses within the EP_RAM to be recalculated. This is a multi-cycle process. At the
end, the EP_RLZED bit will be set in USBDevIntSt (
). USBMaxPSize array
indexing is shown in
. USBMaxPSize is a read/write register.
[1]
Reset value for EP0 and EP1. All other endpoints have a reset value of 0x0.
9.5 USB transfer registers
The registers in this group are used for transferring data between endpoint buffers and
RAM in Slave mode operation. See
Section 13–13 “Slave mode operation”
9.5.1 USB Receive Data register (USBRxData - 0xE010 C218)
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.
Table 143. USB MaxPacketSize register (USBMaxPSize - address 0xE010 C24C) bit
description
Bit
Symbol
Description
Reset value
9:0
MPS
The maximum packet size value.
31:10
-
Reserved, user software should not write ones to reserved
bits. The value read from a reserved bit is not defined.
NA
The Endpoint Index is set via the USBEpIn register. MPS_EP0 to MPS_EP31 are accessed via the
USBMaxPSize register.
Fig 42. USB MaxPacketSize register array indexing
ENDPOINT INDEX
MPS_EP0
MPS_EP31
Table 144. USB Receive Data register (USBRxData - address 0xE010 C218) bit description
Bit
Symbol
Description
Reset value
31:0
RX_DATA
Data received.
0x0000 0000