
Universal Serial Bus Interface – On-The-Go Module
21-50
Freescale Semiconductor
21.5.2.1.2
Current dTD Pointer (Offset = 0x4)
The device controller uses the current dTD pointer to locate transfer in progress. This word is for USB
OTG (hardware) use only and should not be modified by DCD software.
21.5.2.1.3
Transfer Overlay (Offset = 0x8–0x20)
The seven longwords in the overlay area represent a transaction working space for the device controller.
The general operational model is that the device controller can detect whether the overlay area contains a
description of an active transfer. If it does not contain an active transfer, it does not read the associated
endpoint.
After an endpoint is readied, the dTD is copied into this queue head overlay area by the device controller.
Until a transfer expires, software must not write the queue head overlay area or the associated transfer
descriptor. When the transfer is complete, the device controller writes the results back to the original
transfer descriptor and advance the queue.
29
ZLT
Zero length termination select. This bit is ignored in isochronous transfers.
Clearing this bit enables the hardware to automatically append a zero length packet when the following
conditions are true:
• The packet transmitted equals maximum packet length
• The dTD has exhausted the field Total Bytes
After this the dTD retires. When the device is receiving, if the last packet length received equals the maximum
packet length and the total bytes is zero, it waits for a zero length packet from the host to retire the current dTD.
Setting this bit disables the zero length packet. When the device is transmitting, the hardware does not append
any zero length packet. When receiving, it does not require a zero length packet to retire a dTD whose last packet
was equal to the maximum packet length packet. The dTD is retired as soon as Total Bytes field goes to zero,
or a short packet is received.
0 Enable zero length packet (default).
1 Disable the zero length packet.
Note: Each transfer is defined by one dTD, so the zero length termination is for each dTD. In some software
application cases, the logic transfer does not fit into only one dTD, so it does not make sense to add a zero
length termination packet each time a dTD is consumed. On those cases we recommend to disable the
ZLT feature, and use software to generate the zero length termination.
28–27
Reserved. Reserved for future use and must be cleared.
26–16
Maximum
Packet Length
Maximum packet length. This directly corresponds to the maximum packet size of the associated endpoint
(wMaxPacketSize). The maximum value this field may contain is 0x400 (1024).
15
IOS
Interrupt on setup (IOS). This bit used on control type endpoints indicates if USBSTS[UI] is set in response to a
setup being received.
14–0
Reserved. Reserved for future use and must be cleared.
Table 21-43. Current dTD Pointer
Field
Description
31–5
Current dtd
Current dtd. This field is a pointer to the dTD represented in the transfer overlay area. This field is modified by the
device controller to next dTD pointer during endpoint priming or queue advance.
4–0
Reserved. Reserved for future use and must be cleared.
Table 21-42. Endpoint Capabilities/Characteristics (continued)
Field
Description
MCF5329 Reference Manual, Rev 3
Summary of Contents for MCF5329
Page 106: ...ColdFire Core 3 32 Freescale Semiconductor MCF5329 Reference Manual Rev 3...
Page 148: ...Cache 5 22 Freescale Semiconductor MCF5329 Reference Manual Rev 3...
Page 154: ...Static RAM SRAM 6 6 Freescale Semiconductor MCF5329 Reference Manual Rev 3...
Page 184: ...Power Management 8 18 Freescale Semiconductor MCF5329 Reference Manual Rev 3...
Page 204: ...Reset Controller Module 10 8 Freescale Semiconductor MCF5329 Reference Manual Rev 3...
Page 220: ...System Control Module SCM 11 16 Freescale Semiconductor MCF5329 Reference Manual Rev 3...
Page 228: ...Crossbar Switch XBS 12 8 Freescale Semiconductor MCF5329 Reference Manual Rev 3...
Page 268: ...General Purpose I O Module 13 40 Freescale Semiconductor MCF5329 Reference Manual Rev 3...
Page 392: ...SDRAM Controller SDRAMC 18 30 Freescale Semiconductor MCF5329 Reference Manual Rev 3...
Page 436: ...Fast Ethernet Controller FEC 19 44 Freescale Semiconductor MCF5329 Reference Manual Rev 3...
Page 594: ...FlexCAN 23 30 Freescale Semiconductor MCF5329 Reference Manual Rev 3...
Page 678: ...Pulse Width Modulation PWM Module 26 22 Freescale Semiconductor MCF5329 Reference Manual Rev 3...
Page 684: ...Watchdog Timer Module 27 6 Freescale Semiconductor MCF5329 Reference Manual Rev 3...
Page 704: ...DMA Timers DTIM0 DTIM3 29 12 Freescale Semiconductor MCF5329 Reference Manual Rev 3...
Page 754: ...UART Modules 31 34 Freescale Semiconductor MCF5329 Reference Manual Rev 3...
Page 770: ...I2 C Interface 32 16 Freescale Semiconductor MCF5329 Reference Manual Rev 3...
Page 866: ...Debug Module 36 50 Freescale Semiconductor MCF5329 Reference Manual Rev 3...