Maxim Integrated MAXQ622 - Manual (Page 187)

MAXQ612/MAXQ622 User’s Guide
Maxim Integrated 12-17
12.5.2 USB Example 2: Writing to an Internal USB Register (EP2BC)
To write to the USB state registers, the user will write the destination register offset to UADDR, write data to UDATA
register, and wait for UBUSY to clear to complete the operation .
;; writing to USB register
MOV UADDR, #EP2BC
; Read EP2BC register, #EP2BC = 12h
; (RW=0, ADDR=10010
MOV UDATA, #0010h ; Write 0010h to the EP2BC register
CHK: MOV C, UADDR.6 ; Loop to check UBUSY flag
JUMP NC, CHK ; and wait for it to clear
Figure 12-5. Writing to an Internal USB Register
CPU_CLK
CPU WRITE
REG_ADDR1
CPU WRITE
UDATA1
SET UBUSY = 1
CPU READS
UBUSY = 0 CPU WAIT
UADDR[4:0]
UDATA[7:0]
USBRW
UBUSY
SIE_CLK
SIE_DATA[7:0]
SIE_UBUSY
REG_ADDR1
UDATA1
UDATA1
CLEARS CPU UBUSY
SIE WRITES
UDATA1