Browse Prior Art Database

EFFICIENT REVERSE MESSAGE SCROLLING IN A PORTABLE COMMUNICATIONS DEVICE

IP.com Disclosure Number: IPCOM000008202D
Original Publication Date: 1997-Jun-01
Included in the Prior Art Database: 2002-May-27
Document File: 3 page(s) / 137K

Publishing Venue

Motorola

Related People

Charlie Mellone: AUTHOR [+3]

Abstract

Today, many alphanumeric pagers lack the ability to incrementally scroll back in a message. The main reason for lacking the feature is not due to user interface constraints, as one may expect. It is primarily due to the high software implementation cost. The typical implementation requires the software to store the reverse scrolling control information along with the stored message data. This reduced the pagers message storage capacity, sometimes as much as 10%. This paper presents an alternative implementation which reduces the RAM cost (overhead) of the implementation to less than 1% while minimally impacting ROM and execution time.

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EFFICIENT REVERSE MESSAGE SCROLLING IN A PORTABLE COMMUNICATIONS DEVICE

by Charlie Mellone, Tom Klein and Sajid Dalvi

1 INTRODUCTION

  Today, many alphanumeric pagers lack the ability to incrementally scroll back in a message. The main reason for lacking the feature is not due to user interface constraints, as one may expect. It is primarily due to the high software implementation cost. The typical implementation requires the software to store the reverse scrolling control information along with the stored message data. This reduced the pagers message storage capacity, sometimes as much as 10%. This paper presents an alternative implementation which reduces the RAM cost (overhead) of the implementation to less than 1% while minimally impacting ROM and execution time.

2 BACKGROUND

  Pagers or portable information receivers are being used to transfer more and more data to the end user. This information is not only limited to personal messages but also includes data services like news, stock quotes and weather reports. These services are displayed to the user as large messages, typically in the hundreds of characters. While reading these large messages, a pager user often hastily passes an interesting piece of information and would like to go back to re-read a portion of the message. A simple reverse scrolling feature is there- fore desirable in such a product.

  Users of many portable communications devices as well as computers are accustomed to this reverse scrolling feature. As hypertext, HThIL

(web documents), JAVATM and AirScriptTM are implemented in pagers, the need for fast, efficient message traversal will also become unavoidable.

3 TRADITIONAL IMPLEMENTATION

  Often times it is not possible to predict the length of messages received by a portable communicator product. A typical pager receives messages of only 10 to 20 characters while other times an information service arrives with over 200 characters. The message storage implementation must allow for this variation without wasting exces- sive RAM or consuming excessive processor execution resources.

  Accommodating this wide variation of message size is typically implemented using a linked list data structure. A linked list is composed of fixed-sized nodes with node pointers hnking the nodes together to form a message. This limits the wasted RAM to a maximum of N-l, where N is the node size. A typical single-linked node is shown in Figure 1.

Fig. 1 A Single-Linked Node

143 June 1997

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An example of 4 node single-lied message is shown in Figure 2.

Start of Message

  Dynamic...