DS1557 Maxim, DS1557 Datasheet
DS1557
Available stocks
Related parts for DS1557
DS1557 Summary of contents
Page 1
... DQ3 14 DQ2 15 DQ1 16 DQ0 X1 GND V 17 GND PowerCap Module Board (Uses DS9034PCX PowerCap) PIN DESCRIPTION A0–A18 DQ0–DQ7 IRQ/FT RST GND X1 BAT DS1557 34 A18 Maxim 33 A17 32 A14 31 A13 30 A12 29 A11 28 A10 ...
Page 2
... The DS1557 power-on reset can be used to detect a system power down or failure and hold the CPU in a safe reset state until normal power returns and stabilizes; the RST output is used for this function ...
Page 3
... PF DATA READ MODE The DS1557 is in the read mode whenever CE (chip enable) is low and WE (write enable) is high. The device architecture allows ripple-through access to any valid address location. Valid data will be available after the last address input is stable, providing that CE and OE access times are ...
Page 4
... DATA WRITE MODE The DS1557 is in the write mode whenever WE and CE are in their active state. The start of a write is referenced to the latter occurring transition CE. The addresses must be held valid throughout the cycle. CE and WE must return inactive for a minimum of t read or write cycle. Data in must be valid t afterward ...
Page 5
CLOCK OPERATIONS Table 2 and the following paragraphs describe the operation of RTC, alarm, and watchdog functions. Table 2. Register Map ADDRESS 7FFFFh 10 Year 7FFFEh X X 7FFFDh X X 7FFFCh X FT 7FFFBh X ...
Page 6
... The OSC bit is the MSB of the Seconds Register (B7 of 7FFF9h). Setting stops the oscillator, setting starts the oscillator. The DS1557 is shipped from Maxim with the clock oscillator turned off, OSC bit set READING THE CLOCK When reading the RTC data recommended to halt updates to the external set of double-buffered RTC Registers ...
Page 7
... The alarm can be programmed to activate on a specific day of the month or repeat every day, hour, minute, or second. It can also be programmed to go off while the DS1557 is in the battery-backed state of operation to serve as a system wakeup. Alarm mask bits AM1 to AM4 control the alarm mode. Table 3 shows the possible settings ...
Page 8
Figure 3. Clearing IRQ Waveforms The IRQ/FT pin can also be activated in the battery-backed mode. The IRQ/FT will go low if an alarm occurs and both ABE and AE are set. The ABE ...
Page 9
USING THE WATCHDOG TIMER The watchdog timer can be used to detect an out-of-control processor. The user programs the watchdog timer by setting the desired amount of timeout into the 8-bit Watchdog Register (Address 7FFF7h). The five Watchdog Register bits ...
Page 10
... Soldering Temperature (reflow)………………………………………………………………………………………. +260°C This is a stress rating only and functional operation of the device at these or any other conditions above those indicated in the operation sections of this specification is not implied. Exposure to absolute maximum rating conditions for extended periods of time may affect reliability. OPERATING RANGE ...
Page 11
DC ELECTRICAL CHARACTERISTICS (V = 3.3V ±10 Over the Operating Range PARAMETER Active Supply Current TTL Standby Current ( CMOS Standby Current (CE V - 0.2V) CC Input Leakage Current (Any Input) ...
Page 12
AC CHARACTERISTICS—READ CYCLE (T = Over the Operating Range) A PARAMETER Read Cycle Time Address Access Time Low-Z CE Access Time CE Data Off Time Low-Z OE Access Time OE Data Off Time Output ...
Page 13
... Figure 6. Write Cycle Timing, Write-Enable Controlled Figure 7. Write Cycle Timing, Chip-Enable Controlled DS1557 4Meg, Nonvolatile, Y2K-Compliant Timekeeping RAM ...
Page 14
POWER-UP/DOWN CHARACTERISTICS— 5.0V ±10 Over the Operating Range PARAMETER Before IH Power-Down V Fall Time PF(MAX) PF(MIN) V Fall Time ...
Page 15
POWER-UP/DOWN CHARACTERISTICS—3. 3.3V ±10 Over the Operating Range PARAMETER Before IH Power-Down V Fall Time PF(MAX) PF(MIN) V Rise Time ...
Page 16
... The IRQ/FT and RST outputs are open drain. 6) Data-retention time is at +25C. 7) Maxim recommends that PowerCap Module bases experience one pass through solder reflow oriented with the label side up (“live-bug”). 8) Hand soldering and touch-up: Do not touch or apply the soldering iron to leads for more than 3 seconds ...
Page 17
... 2010 Maxim Integrated Products DS1557 4Meg, Nonvolatile, Y2K-Compliant Timekeeping RAM DESCRIPTION parameter in the DC Electrical ...