Datasheet

ATA/ATAPI Interface Port
11−27
SLLS535E − March 2008 TUSB6250
11.6.18 ULRCVEXCNT: Ultra Receive Extra Word Count Register (XDATA at F0F9)
76543210
RSV RSV RSV RSV WORDCN3 WORDCN2 WORDCN1 WORDCN0
R/O R/O R/O R/O R/O R/O R/O R/O
BIT
NAME RESET FUNCTION
3−0 WORDCN[3:0] 0h Ultra receive extra word count.
The value in this register indicates the word count of the extra number of words received
between the TUSB6250 pausing and terminating a UDMA read transfer after the expected
byte count is received. Based on the ATA/ATAPI-5 specification, the ATA/ATAPI device may
send 1, 2, or 3 words (up to 6 bytes) of data after the host pauses the UDMA read transfer.
Although it should not happen, in case WORDCN[3:0] returns 0Fh (15 words) for read, it only
means the TUSB6250 receives at least 15 words, because the counter stops counting after
reaching 0Fh, which is maintained.
The WORDCN[3:0] bits are cleared whenever the MCU sets START_ATAPI or SOFT_RST
in the ATPIFCNFG1 register.
7−4 RSV 0h Reserved