ZENTRUM MIKROELEKTRONIK DRESDEN AG
Datasheet
“ASI for you” IC
The ASI4U is the first IC that supports floating operation of the AS-i receiver and transmitter (within certain lim-
its) in relation to IC ground. Thus far, the ASIN pin always had to be on the same potential like IC ground, pre-
venting full symmetrical input circuits with external coils. The following figures illustrate the new functionality. If
one compares the relation Z1 / Z2, which is a measure for symmetry of the AS-i module input towards machine
ground, it becomes obvious that the new circuit is more symmetrical since Z1 and Z2 are more equal than in the
conventional solution. Please note, that this is not a complete application circuit.
ASI+
ASI+
Z1
AS-i
Slave
IC
GND
Load
Z1
AS-i
Slave
IC
GND
Load
ASI-
Z2
ASI-
Z2
Figure 5:
Conventional application of AS-i IC
with one external coil
Figure 4:
Newly supported application of AS-i IC
with two external coils
2.3.2
IRD communication channel
Besides the AS-i communication channel the ASI4U can also operate on a second input channel, the so called
IRD Input Channel or Addressing Channel. In this mode the IRD pin is input for an AS-i signal in Manchester-II-
coded format. The signal can either be an AC-current signal generated by a photo diode or a 5V-CMOS signal.
The IC automatically detects the type of the signal and switches the input path accordingly.
Output pin in IRD communication mode is LED1. It transmits the slave response as inverted Manchester-II-
coded AS-i signal. The red LED, which is normally connected to LED1, can form the response transmitter in an
optical communication system or LED1 can be directly connected to some external circuitry.
Activation of the IRD communication channel is achieved by a so called magic sequence, that is sent in ad-
vance of the desired communication. The construction of a magic sequence is described in detail in chapter
on page 22. The IRD communication mode is basically left by IC reset, except in
one special case that is also described in that chapter.
2.3.3
Parameter Port Pins
The ASI4U features a 4-bit wide parameter port and a related parameter strobe signal pin PST. There is a de-
fined phase relation between a parameter output event, the parameter input sampling and the activation of the
PST signal. Thus it can be used to trigger external logic or a micro controller to process the received parameter
data or to provide new input data for the AS-i slave response.
AS-i Complete Specification V3.0 newly defines a bidirectional mode for parameter data. The ASI4U supports
this feature, that can be activated by special E²PROM setting.
See chapter
on page 26 for further details.
2.3.4
Data Port Pins
An important feature of the ASI4U is the 8-bit wide data port that consists of a 4-bit wide input section and a 4-
bit wide output section. The input and output sections work independently from each other allowing a maximum
of 8 devices (4 input and 4 output devices) to be connected to the ASI4U. For special applications (compatibil-
ity), the so called Multiplex Mode can be activated that limits the output activation to a certain time frame. Thus,
a 4-bit wide bi-directional data I/O Port can be realized by external connection of the corresponding data input
and output pins.
Copyright © 2006, ZMD AG, Rev.1.4
All rights reserved. The material contained herein may not be reproduced, adapted, merged, translated, stored, or used without the prior written consent of the copyright owner. The
Information furnished in this publication is preliminary and subject to changes without notice.
12/57
ZMD [ Zentrum Mikroelektronik Dresden AG ]
