©

©

©

© 2001 Advanced Linear Devices, Inc., 415 Tasman Drive, Sunnyvale, California 94089-1706, Tel: (408) 747-1155, Fax: (408) 747-1286

ALD523D

12/01

3 of 20

GENERAL DESCRIPTION

The ALD523D is a Multifunction 7-Digit Serial Input

Display Module Controller designed to interface directly

to ALD500 or ALD500R integrating dual slope precision

analog processors as a chip set for building a high

precision and high accuracy analog-to-digital converter

system with auto zero and auto-polarity. The ALD523D

also functions as an universal serial input 7-digit display

module controller that interfaces to most popular industry

standard serial data formats from other microprocessors or

data converters. It is designed for easy setting of industry

standard Character Display Modules (CDM) such as 1-line

by 16-character or 2-line by 16-character LCD or VFD

display modules. The ALD523D is an enhanced version of

the ALD521D digital controller. The ALD523D functions

in three separate operating modes, namely calibrated

reference (mode-A), ratiometric (mode-B), and display

only (mode-C).

The ALD523D digital controller operates as a master

display module controller in either a stand-alone mode or

in an external microprocessor control mode. In the external

microprocessor control mode, the ALD523D can directly

interface with a PC under PC software control via a

standard parallel printer port. This external control mode

is managed by the Serial I/O Interface Logic inside the

ALD523D.

In the stand-alone mode, the ALD523D makes continuous

measurements, and includes all the necessary functions to

fully control a CDM. In the stand-alone mode, ALD523D

operates in conjunction with a 1K EEPROM chip to

preserve the setup parameters and arithmetic (calibration)

parameters of the ALD523D.

The setup and arithmetic parameters are uploaded to the

EEPROM via ALD523D Setup and Calibration PC

software (DVM523). The ALD523D communicates to the

EEPROM on a handshake protocol governed by the

EEPROM Memory Controller inside the ALD523D.

The ALD500/ALD500R dual slope precision analog

processors consist of on-chip digital control circuitry to

accept control inputs, integrating buffer amplifiers, analog

switches, and voltage comparators. It functions in four

operating phases, namely auto zero, integrate, de-integrate,

and integrator zero phases. At the end of a conversion, the

comparator output goes from high to low when the

integrator

crosses

zero

during

de-integration.

ALD500/ALD500R

dual

slope

precision

analog

processors also provide direct logic interface to

ALD523D.

The ALD523D implements the logic and timing for all the

four phases of the ALD500/ALD500R, namely auto zero,

integrate, de-integrate, and integrator zero phases in mode-

A and mode-B operations.

These four phases are

governed by the Dual Slope A/D 4-Phase Controller inside

the ALD523D. The ALD523D operates from an external

clock or its internal oscillator circuit along with an external

crystal. The internal system clock of the ALD523D runs

at a frequency which can be selected at divide-by N (4, 8,

or 64) rate of the crystal (or external) clock frequency.

The ALD523D offers up to 3 display settings, known as

display sets, namely “DGS1”, “DGS2” and “DGS3”.

“DGS1” also has an optional hardware decimal point

setting mode, known as “DGS0”, which allows the user to

use hardware jumper switches to set decimal point

position. Each display set allows a full 7-digit decimal

number to be converted from a 16-bit to 32-bit serial

binary number using the Serial Binary To 6½-Digit

Decimal Converter inside the ALD523D. This 6½-digit

decimal number can also be scaled by a MULTIPLIER

number, and the result of the scaled number displayed on

the CDM through the Display Module Controller within

the ALD523D. Additional display parameters that can be

manipulated are: Digit Blanking, which allows user

selection of number of digits to display; Decimal Point

placement, which controls placement of decimal point, if

any. Up to 3 sets of display UNIT fields are available,

each with a combination of alphanumeric characters up to

8 characters long.

The ALD523D also features hardware control-input pins

for power down (PWRCS), integration time selection (S1,

S2 and S3), data sample averaging (DSA1 and DSA2),

digit blanking (B1 and B2), decimal point placement

(DEC1 and DEC2), zero offset (M and Z), and display set

selection (SEL0 and SEL1). When not used, or if no

control is desired, each of these optional pins are wired to

(DGND), through pull-up or pull-down resistors. The

functions of the control-input pins are managed by the

Control Logic section in the ALD523D.

MODES OF OPERATIONS

The ALD523D functions in either single operating mode

or multiple operating modes, namely calibrated reference

(mode-A), ratiometric (mode-B), and display only (mode-

C). In the single operating mode, ALD523D operates in

one of the three modes of operation, either mode-A, mode-

B or mode-C.

In the multiple operating modes, the

ALD523D can operate interchangeably in each of the three