Preliminary
Registers
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20.9.2.2.17 USB1 Auto Req Register (USB1AUTOREQ)
The USB1 auto req register (USB1AUTOREQ) allows the CPU to enable an automatic IN token request
generation for host mode RX operation per each RX endpoint. This features has the DMA set the
ReqPkt bit in the RXCSR when it clears the RxPktRdy bit after reading out a packet. The ReqPkt bit is
used by the core to generate an IN token to receive data. By using this feature, the host can
automatically generate an IN token after the DMA finishes receiving data and empties an endpoint
buffer, thus receiving the next data packet as soon as possible from the connected device. Without this
feature, the CPU will have to manually set the ReqPkt bit for every USB packet.
There are two modes that Auto Req can function: always or all except an EOP. The always mode will
set the ReqPkt bit after every USB packet the DMA receives thus generating a new IN token after each
USB packet. The EOP mode will set the ReqPkt bit after every USB packet that isn’t an EOP (end of
packet) in the CPPI descriptor. For RNDIS, CDC, and Generic RNDIS modes the auto req will stop
when the EOP is received (either via a short packet for RNDIS,CDC, and Generic RNDIS or the count
is reached for Generic RNDIS), making it useful for starting a large RNDIS packet and having it auto
generate IN tokens until the end of the RNDIS packet. For transparent mode, every USB packet is an
EOP CPPI packet, so the auto req never functions and acts like auto req is disabled.
The USB1 auto req register is shown in
and described in
Figure 20-103. USB1 Auto Req Register (USB1AUTOREQ)
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
Rx(N+14)_
Rx(N+13)_
Rx(N+12)_
Rx(N+11)_
Rx(N+10)_
Rx(N+9)_
Rx(N+8)_
Reserved
autoreq
autoreq
autoreq
autoreq
autoreq
autoreq
autoreq
R-0h
R/W-0h
R/W-0h
R/W-0h
R/W-0h
R/W-0h
R/W-0h
R/W-0h
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
Rx(N+7)_
Rx(N+6)_
Rx(N+5)_
Rx(N+4)_
Rx(N+3)_
Rx(N+2)_
Rx(N+1)_
Rx(N+0)_
autoreq
autoreq
autoreq
autoreq
autoreq
autoreq
autoreq
autoreq
R/W-0h
R/W-0h
R/W-0h
R/W-0h
R/W-0h
R/W-0h
R/W-0h
R/W-0h
LEGEND: R/W = Read/Write; R = Read only; -n = value after reset
Table 20-115. USB1 Auto Req Register (USB1AUTOREQ) Field Descriptions
Bit
Field
Value
Description
31-30
Reserved
0
Always read as 0. Writes have no effect.
29-28
Rx(N+14)_autoreq
RX endpoint N+14 Auto Req enable
00
No auto req
01
Auto req on all but EOP
10
Reserved
11
Auto req always
27-26
Rx(N+13)_autoreq
RX endpoint N+13 Auto Req enable
00
No auto req
01
Auto req on all but EOP
10
Reserved
11
Auto req always
25-24
Rx(N+12)_autoreq
RX endpoint N+12 Auto Req enable
00
No auto req
01
Auto req on all but EOP
10
Reserved
11
Auto req always
23-22
Rx(N+11)_autoreq
RX endpoint N+11 Auto Req enable
00
No auto req
01
Auto req on all but EOP
10
Reserved
11
Auto req always
1912Universal Serial Bus (USB)
SPRUGX9 – 15 April 2011
© 2011, Texas Instruments Incorporated
Содержание TMS320C6A816 Series
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