memory products - Al Kossow's Bitsavers

M8571MASTER TRANSMITS TO SLAVE RECEIVER (WRITE MODE)Is Iacknowtedgefrom lIaveItR/Wacknowledge'rom lIaveI MSBacknowledgefrom slave~L--Iastb~auto incrementmemory word address2) R/W = "1" (READ)In this case the slave acts as transmitter and, therefore,the transmission changes direction. The secondbyte of the sequence will be sent by theM8571 and it will contain the data present in thememory present at the address pointed by the "current"value of the address register. Following byteswill be the data present at the "next" addresses.At the end of each byte, the M8571 places a "1"on the bus during acknowledge time and waits forthe master to send a "0" (meaning "acknowledge").When the master want to stop the transfer, it givesa "1" (not "acknowledged"): as a consequence,the M8571 leaves the bus high so that the mastercan give the stop condition. An example is givenbelow:O. STA1. 10100ss1 A2. xxxxxxxx H (xxxxxxxxisthedatapresentin the currently addressedmemory location; H is the highlevel placed on the bus byM8571)3) MIXED SEQUENCEWhen the master wants to read a memory locationdifferent from the one currently addressed, a longersequence is needed, which includes the writing ofthe address register. The sequence is as follows:O. STA1. 10100ss0 A2. xyyyyyyy A3. STA4. 10100ss1 A5. xxxxxxxx HWhere xxxxxxxx is the data present in the yyyyyyymemory locationAs appears from the example, a start condition canbe given without a previous stop condition.MASTER READS SLAVE IMMEDIATELY AFTER FIRST BYTE (READ MODE)acknowledge acknowledge acknowledge'rom lIave 'rom master 'rom master, 'MSB iI 5 I ~L~VE: A~O~E~ :. H : : :OA:TA: : : H : : : : : : : 11 I p IR/tW L--- n bytes---ij L-- n bytes ~auto incrementword address8/11206