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Steve, Notice that the wording says that the sum of the output and bi-directional resistances. This means add up the driver resistance (usually about 30 Ohms) and the external series resistor value. The values listed in table 7 are only "typical" values. Notice also that on the data lines, the resistors are 33 Ohms on both sides. This is because these lines are bi-directional, and the values were chosen as a compromise for signal termination and DC Voltage High/Low values. I believe that the reason for the requirement that modes greater than mode 4 be the same on data and strobe was a further compromise of optimal termination in favor of matching RC effects and improve timing margin between data and strobe. Perhaps someone else can verify if that is correct. John Masiewicz Senior Technical Staff Advanced Concepts Western Digital 949-672-7686 -----Original Message----- From: Steve Livaccari [mailto:[EMAIL PROTECTED] Sent: Thursday, July 10, 2003 2:15 PM To: [EMAIL PROTECTED] Subject: [t13] UDMA Termination Resistors This message is from the T13 list server. In ATA/ATAPI-7 rev 3 vol2 pdf from on the web in 7.2.3.2 on pdf page 36 ( last line) states strobe and data lines have the same series termination. Table 7 ( next page) states data 33 ohm and strobe 82 ohm. Am I missing something here or is this a typo? If so which is correct? Regards, Steve Livaccari Hard Drive Engineering IBM Global Procurement Internet: [EMAIL PROTECTED] Phone (919) 543.7393
