Real Time Clock Parallel 512KByte 32-Pin DIP Module

The bq4850Y RTC Module is a nonvolatile 4,194,304-bit SRAM organized as 524,288 words by 8 bits with an integral accessible real-time clock. The device combines an internal lithium battery, quartz crystal, clock and power-fail chip, and a full CMOS SRAM in a plastic 32-pin DIP module. The RTC Module directly replaces industry-standard SRAMs and also fits into many EPROM and EEPROM sockets without any requirement for special write timing or limitations on the number of write cycles. Registers for the real-time clock, alarm and other special functions are located in registers 7FFF8h– 7FFFFh of the memory array. The clock and alarm registers are dual-port read/write SRAM locations that are updated once per second by a clock control circuit from the internal clock counters. The dual-port registers allow clock updates to occur without interrupting normal access to the rest of the SRAM array. The bq4850Y also contains a powerfail-detect circuit. The circuit deselects the device whenever VCC falls below tolerance, providing a high degree of data security. The battery is electrically isolated when shipped from the factory to provide maximum battery capacity. The battery remains disconnected until the first application of VCC.

• Integrated SRAM, real-time clock, crystal, power-fail control circuit, and battery
• Real-Time Clock counts seconds through years in BCD format
• RAM-like clock access
• Pin-compatible with industrystandard 512K x 8 SRAMs
• Unlimited write cycles
• 10-year minimum data retention and clock operation in the absence of power
• Automatic power-fail chip deselect and write-protection
• Software clock calibration for greater than ±1 minute per month accuracy