ald523d Advanced Linear Devices Inc (ALD), ald523d Datasheet - Page 12

• Manufacturer Part Number: ald523d
• Description: Multifunction 7-digit Serial Input Display Module Controller
• Manufacturer: Advanced Linear Devices Inc (ALD)

POWER UP AND POWER DOWN
Upon power up or power-on-reset, the ALD523D
initializes all internal counters, registers, I/O ports, and the
CDM. Then it reads the setting of the control-input pins,
and sets up the mode of operation as programmed by
instructions preset by the user in the EEPROM memory.
When the mode of operation has not been preset, a
message “PROGRAM MEMORY” is displayed on the
CDM. Next, it checks the status of the PWRCS pin.
A logical “0” state on PWRCS pin powers up the
ALD523D, and a logical “1” state on the PWRCS pin
powers down the ALD523D as well as the ALD500R
(mode-A) and blanks the CDM (in both mode-A and
mode-B). The crystal oscillator circuit of the ALD523D is
also stopped. To start and power up the ALD523D again,
simply put a logical 0 state on the PWRCS pin.
external microprocessor can therefore utilize this pin to
control the ALD523D power-on status. If power down
feature is not used, then the PWRCS pin must be grounded
through pull-down resistor to leave the ALD523D in
continuously power-on mode.
REFERENCE CALIBRATION MODE
The ALD523D is designed to interface directly to the
ALD500 or ALD500R integrating dual slope precision
analog processors and work together as a chip set. One of
the beneficial features of the ALD500R to the ALD500 is
its precision internal voltage reference, which eliminates
the need of introducing an external reference voltage to the
conversion system, for equal or improved system
performance along with reduced component count and
cost.
The block diagram of the reference calibration mode is
shown in figure 6. Unlike many external reference voltage
circuits where reference voltage calibration is performed
by tweaking trimmer pots, the internal reference voltage
calibration is performed through the use of software
calibration method, i.e. DVM523.EXE (see Calibrate
Reference Voltage (#3 Key) section in the ALD523D
Setup and Calibration Software User Guide).
Upon power up or during normal running condition, the
ALD523D continuously checks the status of the control-
input pins 18 and 12, namely DVCS and CAL,
respectively for entering setup and calibration modes. A
logical “1” state on DVCS pin and a logical “0” on CAL
pin instruct the ALD523D to enter the reference
calibration mode.
ALD523D
© © © © 2001 Advanced Linear Devices, Inc., 415 Tasman Drive, Sunnyvale, California 94089-1706, Tel: [phone], Fax: [phone]
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An
Upon entering reference calibration mode, measurement
data on the ALD523D is transmitted serially to the PC via
SCLK and DATOUT pins. The ALD523D sets the SCLK
pin to logic “0” state with the first bit of the serial data
transmitted simultaneously via DATOUT pin. The PC
reads the first bit on DATOUT and sends a serial clock
pulse on the DVCS line as the acknowledge signal. This
serial data read process continues for the rest of the 24
serial bits with alternatively sending serial clock pulses on
every bit read, until SCLK is set to logic “1” state after 24
clock cycles.
The 24-bit serial word corresponding to 24 serial clock
pulses consists of a 23-bit binary word with MSB as the
first bit and LSB the 23
last bit. The sign bit is set as logical “1” as a positive sign,
and logical “0” as a negative sign.
Calibration mode can also be used as serial output port
mode, where the output binary word can be clocked out by
any PC, device or microprocessor having access to CAL,
SCLK, DATOUT, and DVCS pins.
The detail calibration timing is shown in “ALD523D to PC
Mode-A Reference Calibration Timing” section of this
data sheet. When CAL pin is set to high at the end of
calibration mode, the ALD523D returns to its normal
continuous running mode.
Figure 6. Reference calibration mode block diagram.
PC
ANALOG
ALD500R
INPUT
rd
bit, followed by a sign bit as the
ALD523D
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