Nxp Semiconductors UM10237 User Manual
UM10237_2
© NXP B.V. 2008. All rights reserved.
User manual
Rev. 02 — 19 December 2008
346 of 792
NXP Semiconductors
UM10237
Chapter 13: LPC24XX USB device controller
9.5 Endpoint realization registers
The registers in this group allow realization and configuration of endpoints at run time.
9.5.1 EP RAM requirements
The USB device controller uses a RAM based FIFO for each endpoint buffer. The RAM
dedicated for this purpose is called the Endpoint RAM (EP_RAM). Each endpoint has
space reserved in the EP_RAM. The EP_RAM space required for an endpoint depends
on its MaxPacketSize and whether it is double buffered. 32 words of EP_RAM are used by
the device for storing the endpoint buffer pointers. The EP_RAM is word aligned but the
MaxPacketSize is defined in bytes hence the RAM depth has to be adjusted to the next
word boundary. Also, each buffer has one word header showing the size of the packet
length received.
dedicated for this purpose is called the Endpoint RAM (EP_RAM). Each endpoint has
space reserved in the EP_RAM. The EP_RAM space required for an endpoint depends
on its MaxPacketSize and whether it is double buffered. 32 words of EP_RAM are used by
the device for storing the endpoint buffer pointers. The EP_RAM is word aligned but the
MaxPacketSize is defined in bytes hence the RAM depth has to be adjusted to the next
word boundary. Also, each buffer has one word header showing the size of the packet
length received.
The EP_ RAM space (in words) required for the physical endpoint can be expressed as
where dbstatus = 1 for a single buffered endpoint and 2 for double a buffered endpoint.
Table 315. USB Endpoint Interrupt Priority register (USBEpIntPri - address 0xFFE0 C240) bit allocation
Reset value: 0x0000 0000
Bit
31
30
29
28
27
26
25
24
Symbol
EP15TX
EP15RX
EP14TX
E14RX
EP13TX
EP13RX
EP12TX
EP12RX
Bit
23
22
21
20
19
18
17
16
Symbol
EP11TX
EP11RX
EP10TX
EP10RX
EP9TX
EP9RX
EP8TX
EP8RX
Bit
15
14
13
12
11
10
9
8
Symbol
EP7TX
EP7RX
EP6TX
EP6RX
EP5TX
EP5RX
EP4TX
EP4RX
Bit
7
6
5
4
3
2
1
0
Symbol
EP3TX
EP3RX
EP2TX
EP2RX
EP1TX
EP1RX
EP0TX
EP0RX
Table 316. USB Endpoint Interrupt Priority register (USBEpIntPri - address 0xFFE0 C240) bit description
Bit
Symbol
Value
Description
Reset value
31:0
See
USBEpIntPri
bit allocation
table above
USBEpIntPri
bit allocation
table above
0
The corresponding interrupt is routed to the EP_SLOW bit of USBDevIntSt
0
1
The corresponding interrupt is routed to the EP_FAST bit of USBDevIntSt
EPRAMspace
MaxPacketSize
3
+
4
--------------------------------------------------
1
+
⎝
⎠
⎛
⎞
dbstatus
×
=