2003/9/1

5

ES51963

4 1/2 DMM

Operation Mode

(1) Operation of ES51963 and the external microprocessor

ES51963 is a microprocessor based data acquisition ADC. ES51963 performs A-to-D

conversion and the microprocessor acquires the results via interface pins: SCLK, EOC and

STATUS. There are two formats for data acquisition. In format 1, ES51963 raises the logic

level of EOC to high during the integration phase (INT) and de-integration phase (DINT).

The microprocessor can acquire the conversion result by counting the time period as EOC is

high. And the microprocessor can obtain the operation status of ES51963 such as conversion

rate, buzzer frequency, sign bit, etc. from pin STATUS. The value of STATUS is read in

serial with clock pin, SCLK which is controlled by microprocessor.

In addition to counting the time period of EOC, ES51963 provides another way, the

format 2 to obtain the conversion result. In format 2 the conversion result is computed by

ES51963 itself and the microprocessor can obtain the output count from pin STATUS.

The decision to choose format 1 or format 2 depends on application. Format 2 is

simple for general application. On the other hand, a microprocessor must set up a timer to

estimate the duration of EOC in format 1. Thus the maximum count or resolution could be

changed by choosing the counting frequency of the timer. For example the maximum counts

of ES51963 operating in format 2 with 4 MHz operating clock is 22,000. The same

resolution is obtained in format 1 with timer counting period, 2 us/count. A higher

resolution, say 44,000 counts, could be achieved by speeding up the counting frequency

twice.

In addition to change operation format, ES51963 allow a user to change the

conversion rate, buzzer frequency on the fly. Their changing methods will be described in

following sections.

(2) Buzzer frequency

ES51963 provides buzzer output at pin BUZout. The pin BUZin (active high) is used

to control whether BUZout should output buzzer wave or not. The default buzzer frequency

is 2 KHz with 4 MHz operating frequency (crystal oscillator frequency at pins OSC1 and

OSC2).

ES51963 provides eight buzzer frequency selection options and the external micro-

processor can choose one frequency that is audible by setting the values of bits, B2, B1 and

B0 in the STATUS word used in communication between ES51963 and the external

microprocessor. The communication protocol will be described in detail in section (6). The