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CDP1879E Datasheet(PDF) 6 Page - Intersil Corporation |
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CDP1879E Datasheet(HTML) 6 Page - Intersil Corporation |
6 / 18 page 4-109 General Operation The real-time clock contains seconds, minutes, and hours, date and month counters that hold time of day/calendar information (see Figure 2). The frequency of an intrinsic oscillator is divided down to supply a once-a-second signal to the counter series string. The counters are separately addressable and can be written to or read from. The real-time clock contains seconds, minutes and hour write-only alarm latches that store the alarm time (see Fig- ure 3). When the value of the alarm latches and counters are equal, the interrupt output is activated. The interrupt output can also be activated by a clock output transition. The clock output is derived from the prescaler and counters and can be one of 15 square-wave signals. The value in the read- only interrupt status register identifies the interrupt source. Operational control of the real-time clock is determined by the byte in a write-only control register. The 8-bit value in this register determines the correct divisor for the prescaler, a data direction and alarm enable bit, clock output select, and start/stop control (see Figure 4). Data transfer and addressing are accomplished in two modes of operation, memory mapping and I/O mapping using the CDP1800-series microprocessors. The mode is selected by the level on an input pin. (IO/MEM). Memory mapping implies use of the address lines as chip selects and address inputs during linear selection or partial or full decod- ing methods. I/O mapping with the CDP1800-series micro- processors involves use of the N line outputs in conjunction with input and output instructions to transfer data to and from memory. REGISTER TRUTH TABLE ADDRESS ACTIVE SIGNAL BIT 3 CONTROL REGISTER REGISTER OPERATION A2 A1 AO TPB/WR RD 0 1 0 X - 0 Write Seconds Counter 0 1 0 - X 0 Read Seconds Counter 0 1 1 X - 0 Write Minutes Counter 0 1 1 - X 0 Read Minutes Counter 1 0 0 X - 0 Write Hours Counter 1 0 0 - X 0 Read Hours Counter 1 0 1 X - 0 Write Date Counter 1 0 1 - X 0 Read Date Counter 1 1 0 X - 0 Write Month Counter 1 1 0 - X 0 Read Month Counter 0 1 0 X - 1 Write Seconds Alarm Latch 0 1 1 X - 1 Write Minutes Alarm Latch 1 0 0 X - 1 Write Hours Alarm Latch 1 1 1 X - - Write Control Register 1 1 1 - X - Read Int. Status Register CDP1879, CDP1879C-1 |
Similar Part No. - CDP1879E |
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Similar Description - CDP1879E |
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