Interfacing DS1318 with 8051 Microcontroller

This application note demonstrates how to use the DS1318 elapsed time counter to count days. The software example includes basic operation procedures and gives a schematic diagram of the application circuit.

BEGIN: DB HTML DS1318 pin configuration

Counter Overview

This application note demonstrates how to use the DS1318 elapsed time counter, which has a 44-bit counter that provides a timing resolution of 244µs. The 44-bit counter is accessed through six 8-bit registers (Figure 1).

Figure 1. DS1318 44-bit counter configuration.

Conceptually, the 44-bit counter can be divided into a 12-bit subsecond counter and a 32-bit counter with a resolution of one second (Figure 2). If the application does not require subsecond resolution, the 32-bit seconds counter can be accessed.

Figure 2. 12-bit subsecond counter and 32-bit seconds counter.

In the example provided in this application note, a software routine continuously reads the value of a 32-bit seconds counter once per second and outputs the time and date in ASCII format through the UART interface of an 8051 microcontroller (µC). The time and date are based on the elapsed time in seconds since 00:00:00, January 1, 1970. 0000000h corresponds to 00:00:00, January 1, 1970; 42C924C0h corresponds to 2005/7/4 12:00:00.

Another subroutine configures the device to interrupt periodically with a frequency of 1Hz. Each time an interrupt occurs, the interrupt handler reads the counter data, converts the time into a date format, and outputs the data in ASCII format through URAT.

We also provide other routines that can perform the following operations on the DS1318: write user input data to registers; convert the time and date entered by the user to the time in seconds since January 1, 1970; write data to a counter. Another subroutine is used to read the DS1318 registers and output the data in hexadecimal format.

How it works

The hardware circuit in this application note places the data of the DS1318 into the data memory space of the µC. The µC accesses the DS1318 registers by reading and writing the data memory at the correct address.

The DS80C323 low-voltage, 8051-compatible microcontroller is used in this example. Both user input data and program output data are passed to the µC, communicating through the RS-232 interface of a PC terminal emulator. Detailed information on the DS80C323 microcontroller used in this application note can be downloaded from the company's website.

The program listing is shown in Figure 3, and the circuit schematic is shown in Figure 4.

Figure 3. Program listing

Figure 4. Circuit schematic.