Rainbow-electronics DS1990A Manual do Utilizador

1 of 10 081999DS1990A SPECIAL FEATURES§ Upgrade of DS1990 allows multiple SerialNumber iButtons to reside on a common bus§ Unique 48–bit serial n

DS1990A10 of 10NOTES:1. All voltages are referenced to ground.2. VPUP = external pullup voltage.3. Input load is to ground.4. An additional reset

DS1990A2 of 10iButton DESCRIPTIONThe DS1990A Serial Number iButton is a rugged data carrier that acts as an electronic registrationnumber for automa

DS1990A3 of 10DS1990A MEMORY MAP Figure 18-Bit CRC Code 48-Bit Serial Number 8-Bit Family Code (01h)MSB LSB MSB LS

DS1990A4 of 10TRANSACTION SEQUENCEThe sequence for accessing the DS1990A via the 1-Wire port is as follows:§ Initialization§ ROM Function Command§

DS1990A5 of 10ROM FUNCTIONS FLOW CHART Figure 4

DS1990A6 of 101-WIRE SIGNALINGThe DS1990A requires strict protocols to ensure data integrity. The protocol consists of four types ofsignaling on one

DS1990A7 of 10READ/WRITE TIMING DIAGRAM Figure 6Write-One Time Slot60 µs ≤ tSLOT < 120 µs1 µs ≤ tLOW1 < 15 µs1 µs ≤ tREC < ∞Write-Zero Tim

DS1990A8 of 10CRC ASSEMBLY LANGUAGE PROCEDURE Table 1DO_CRC:CRC_LOOP:ZERO:PUSH ACCPUSH BPUSH ACCMOV B,#8XRL A,CR

DS1990A9 of 10ABSOLUTE MAXIMUM RATINGS*Voltage on any Pin Relative to Ground -0.5V to +7.0VOperating Temperature -40°C to +85°CStorage Temperature