Maxim Integrated MAXQ622 - Manual (Page 175)

MAXQ612/MAXQ622 User’s Guide
Maxim Integrated 12-5
Note: Writes to this register are ignored when UBUSY = 1.
12.3.2 USB Data Register (UDATA)
This register is used for supplying data for supported USB register write operation request and for returning data for
USB register read operation .
Bits 7 to 0: USB Data Register (UDATA[7:0]). These data register bits are used for supplying data for supported USB
register write operation request and for returning data for USB register read operation .
12.4 USB SIE Internal Register Descriptions
The internal control and data registers are accessed through the UADDR and UDATA registers as previously described .
These internal registers control all aspects of the SIE .
12.4.1 Function Address Register (FNADDR)
Note: Read access only when USBEN = 1. Reading the function address before USBEN = 1 can compromise USB functionality.
Bit 7: Reserved. Reads returns zero.
Bits 6 to 0: USB Register Address (FNADDR[6:0]). These register bits represent a unique value that identifies the
USB function . Upon reset and power-up, the address bits are defaulted to zero and are set by host during the enumera-
tion process . The address zero is reserved as the default value and cannot be assigned to any function . This register
also is cleared to 00h by a USB bus reset . The SIE updates this register after receiving the ACK handshake at the
conclusion of a Set_Address request from the host .
Register Name UDATA
Register Description USB Data Register
Register Address M4[05h]
Register Name FNADDR
Register Description Function Address Register
Register Address UADDR[4:0] = 01h
Bit # 7 6 5 4 3 2 1 0
Name UDATA7 UDATA6 UDATA5 UDATA4 UDATA3 UDATA2 UDATA1 UDATA0
Reset 0 0 0 0 0 0 0 0
Access rw rw rw rw rw rw rw rw
Bit # 7 6 5 4 3 2 1 0
Name — FNADDR6 FNADDR5 FNADDR4 FNADDR3 FNADDR2 FNADDR1 FNADDR0
Reset 0 0 0 0 0 0 0 0
Access r r r r r r r r