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12-24 Intel® PXA255 Processor Developer’s Manual
USB Device Controller
12.6.2 UDC Control Function Register (UDCCFR)
The UDC Control Function register (UDCCFR) contains 1 mode bit and 1 enable bit that lets
software delay sending back an ACK response to SET_CONFIG or SET_INTERFACE commands
from the host. The remaining bits are reserved.
12.6.2.1 ACK Control Mode
The ACK control mode (ACM) bit enables user control of the ACK response to the status IN
requests of SET_CONFIGURATION and SET_INTERFACE commands. When ACM is set to 0,
the UDC automatically responds to the STATUS IN request following a SET_CONFIGURATION
and SET_INTERFACE with an ACK. When ACM is set to 1, the UDC responds to the STATUS
IN request following a SET_CONFIGURATION and SET_INTERFACE command with a NAK
until AREN is set to 1. When the user sets AREN to 1, the UDC responds with an ACK to the next
STATUS IN request.
12.6.2.2 ACK Response Enable
When ACM = 1, the ACK response enable (AREN) bit enables user control of the ACK response
to the status IN requests of SET_CONFIGURATION and SET_INTERFACE commands. When
ACM is set to 1, the UDC responds to the STATUS IN request following a
Table 12-13. UDC Control Function Register
0x 4060_0008 UDCCFR USB Device Controller
Bit
32 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
Reserved
AREN
MB1
ACM
MB1
Reset X X X X X X X X X X X X X X X X X X X X X X X X X 1 1 1 1 1 1 1 1
Bits Name Description
31:8 — Reserved – Read as unknown and must be written as zero.
7AREN
ACK RESPONSE ENABLE (read/write 1 to set)
0 = Send NAK response to SET_CONFIGURATION and SET_INTERFACE
commands
1 = Send ACK response to SET_CONFIGURATION and SET_INTERFACE
commands
6:2 MB1
MB1
This bit must be set to 1.
0 = Reserved
1 = Must be configured to 1.
2ACM
ACK CONTROL MODE (read/write 1 to set)
0 = Send ACK response to SET_CONFIGURATION and SET_INTERFACE
commands with no user intervention (B-step default)
1 = Send NAK response to SET_CONFIGURATION and SET_INTERFACE
commands until UDCCFR[AREN] = 1
1MB1
MB1
This bit must be set to 1.
0 = Reserved
1 = Must be configured to 1.