CHAPTER 6 USB CONTROLLER
Preliminary User’s Manual S15543EJ1V0UM 325
6.2.15 U_CMR (USB Command Register)This register is used for issuing Tx request or adding Rx Buffer Directories to Pool.The VR4120A writes commands into this register.Whenever B bit (Bit 31) is set, the value will not change even if the VR4120A writes commands into this register.
Bits Field R/W Default Description
31 B R/W 0 Busy:
Bit that indicates whether the interpretation of an issued command has
terminated. When the execution of the command has not yet completed, this
bit will be set to a ‘1’. When the execution of a command has completed, this
bit will be set to a ‘0’.
When the VR4120A tries to issue one command immediately after another, it
is necessary to confirm that this bit is set to a ‘0’.
30:27 Reserved R/W 0 Reserved for future use. Writes ‘0’s.
26:24 Command R/W 000 Field for specifying the type of a command. USB Controller's internal
processing varies depending on the value written into this field.
000: Data transmitting at EndPoint0
001: Data transmitting at EndPoint1
010: Data transmitting at EndPoint3
011: Data transmitting at EndPoint5
100: Addition of Buffer Directories to Pool0
101: Addition of Buffer Directories to Pool1
110: Addition of Buffer Directories to Pool2
111: Reserved (Don't Use)
23:16 Reserved R/W 0 Reserved for future use. Writes ‘0’s.
15:0 Data Size/NOD R/W 0 Data Size/Number Of Buffer Directory:
The meaning of this field depends on the value written into the Command
field.
Command = 0xx: VR4120A has to write the size of the transmitting data in
this field.
Command = 100, 101, 110: Indicates the number of Buffer Directories added
to a pool.
Command = 111: This field has no meaning.
6.2.16 U_CA (USB Command Extension Register)This register is used for issuing Tx request or adding Rx Buffer Directories to Pool.The VR4120A writes the start address of either the Tx or the Rx Buffer Directory into this register.
Bits Field R/W Default Description
31:0 Address R/W 0 The meaning of this field varies depending on the value written into the
Command field of the USB Command Register.
Command = 0xx: Start address of the transmit packet
Command = 100, 101, 110: Start address of the Buffer Directory to be added
to the receive pool
Command = 111: This register has no meaning.