DS1221 Dallas, DS1221 Datasheet
DS1221
Available stocks
Related parts for DS1221
DS1221 Summary of contents
Page 1
... DESCRIPTION The DS1221 Nonvolatile Controller x 4 Chip is a CMOS circuit which solves the application problem of converting CMOS RAMs into nonvolatile memories. Incoming power is monitored for an out-of- tolerance condition. ...
Page 2
... During nominal supply conditions the chip enable outputs follow the logic of a 2-to-4 decoder. The fifth function the DS1221 performs is to check battery status to warn of potential data loss. Each time that V power is restored the battery voltage is checked with a precision comparator. If the connected battery voltage is less than 2 volts, the second memory cycle is inhibited ...
Page 3
... TYPICAL APPLICATION Figure 2 SECURITY SEQUENCE Figure 3 OUTPUT LOAD Figure DS1221 ...
Page 4
... CCI V V -0.2 CCO CC I CCO1 4.25 4.37 CCTP SYMBOL MIN TYP V -0.2 V OHL CC V -0.2 BAT I BAT I CCO2 DS1221 ( MAX UNITS NOTES 4.5 to 5.5V) CC MAX UNITS NOTES +1.0 µA +1.0 µ 4.0 ...
Page 5
... I is the maximum average load which the DS1221 can supply to the memories. CCO1 5. Measured with a load as shown in Figure the maximum average load current which the DS1221 can supply to the memories in the CCO2 battery back-up mode. 7. Chip enable outputs - CE0 8 ...
Page 6
... For each of the 64 read cycles, 1 bit of the user-defined read only register is driven onto the DQ line. This phase also requires that the 64 read cycles be consecutive. The data being read from the read only register can be used by software to determine if the DS1221 will be permitted to be used with that particular system. After the 64 subsequent memory cycles will be passed through and will become actual memory accesses based upon address inputs ...
Page 7
... POWER-DOWN Figure 5 POWER-UP Figure DS1221 ...
Page 8
... READ CYCLE TO SECURITY OPTION Figure 7 WRITE CYCLE TO SECURITY OPTION Figure 8 NOTES and t are functions of the first occurring edge function of the latter occurring edge of WR RESET FOR SECURITY OPTION Figure DS1221 ...