EZ-USB FX3 Technical Reference Manual, Document Number: 001-76074 Rev. *F 471
SHDL_EHCI
0xE0032800
10.14.35 SHDL_OHCI (continued)
18:17 MULT[1:0] High-Bandwidth Pipe Multiplier. This field is a multiplier used to key the host controller as the number
of successive packets the host controller may submit to the endpoint in the current execution. This
field should be programmed according to the EPM configuration for that EP. This field will get decre-
mented only if the transfer is successful. If not successful, the original value will be reloaded.
00 Reserved. A zero in this field yields undefined results.
01 One transaction to be issued for this endpoint per micro-frame
10 Two transactions to be issued for this endpoint per micro-frame
11 Three transactions to be issued for this endpoint per micro-frame
16 ISO_EPM 0 For ISO-OUT when EPM is empty for that EP then a ZLP will be issued by TP.
For ISO-IN when EPM is full for that EP then and ISO-IN will be issued.
1 For ISO-OUT when EPM is empty for that EP then that entry will be skipped.
For ISO-IN when EPM is full for that EP then that entry will be skipped.
15:14 CERR[1:0] This field is a 2-bit down counter that keeps track of the number of consecutive Errors detected while
executing this qTD.
If this field is programmed with a nonzero value during setup, the Host Controller decrements the
count and writes it back to the qTD if the transaction fails. If the counter counts from one to zero, the
Host Controller marks the qTD inactive, sets the Halted bit to a one and error status bit for the error
that caused CERR to decrement to zero. An interrupt will be generated if the USB Error Interrupt
Enable bit in the USBINTR register is set to a one. If HCD programs this field to zero during setup, the
Host Controller will not count errors for this qTD and there will be no limit on the retries of this qTD.
13:10 NAK_CNT[1:0] This field is a counter the host controller decrements whenever a transaction for the endpoint associ-
ated with this queue head results in a Nak or Nyet response.
9 HALT This will indicate that the EP is halted.
Skip this qTD and move to next qTD.
8T 0 Not End of the Period/Asynchronous list
1 End of the Period/Asynchronous list
This bit indicates that there are no more valid entries in the current list.
7ZPLEN This field is used only for non-ISO endpoints.
0 Scheduler will set the active bit to zero when the total byte count reaches zero.
1 Scheduler will set the active bit to zero when the total byte count is zero and a ZLP is sent/
received.
6:5 EPT[1:0] The End Point Type.
00 Control
01 Isochronous
10 Bulk
11 Interrupt
4:0 EPND[4:0] [3:0]: EP number, Values: 0-15
[4]: EP Direction, 1: OUT, 0: IN
The direction bit is not used for EP0. Scheduler uses the EP0_code to determine the direction of the
EP0 transaction.
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