Elec2630 Embedded Systems Theory
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ELEC2630 EMBEDDED SYSTEMS THEORY Lecture 10: A Web based Embedded system design & an overview of Memory Types
A Web based Embedded System design
This system uses a conventional PC as a Web server as a user interface The key to this system is the use of a database The PC is often part of a distributed embedded system used for control and data capture The resulting data is stored in the database Any authorised user can have access to the data, searchable and manipulated as
User Interface Software
The code called by the user is in the form of CGI programs The CGI code can be written to process user requests into queries for the database and return the data in the form that the user requires
Data Collection and Control
The code for this part of the task is now totally separate and can be written using the most appropriate programming techniques The embedded system is often distributed and may use devices as the Netiom as part of the control and data collection methods used
Conclusions
The integration of web access with embedded systems takes many forms and is a growth area at the moment This trend is helped by the increasing complexity of embedded devices, such as micro-controllers, made posible by advances in semiconductor technologies
Hardware Review: Memory types
DRAM
This type of memory is used when a large amount of storage is required at low cost. The storage element is a capacitor which can be either charged or not charged. The main problem is that the charge leaks away and has to be replaced before the data is lost. This feature is reflected in the full name of Dynamic Ram. The complexity of the circuitry needed to refresh the data does reduce the cost advantage of the low number of transistors required per bit.
Video RAM
This device is derived from the DRAM A DRAM used as a conventional memory as well as additional hardware to use the data at the same time for the Video display Essentially the hardware consisted of a shift register which converted the parallel data to serial to be clocked out to drive the video display
SRAM
The full name of this device is Static RAM The data is held without refreshing all the time the power is applied The cost per bit is much higher than for DRAM as more transistors are involved in the circuit for each bit The circuit can be designed for low power operation despite the extra devices per bit as the power consumption is low except when switching
FLASH MEMORY
This is non volatile storage, i.e. the data is not lost when the power is removed The circuit uses a single transistor as a storage cell Write operation can take up to several milliseconds, but reads can be as low as 70 to 100 nanoseconds This specification makes it a suitable device for program storage
A Web based Embedded System design
This system uses a conventional PC as a Web server as a user interface The key to this system is the use of a database The PC is often part of a distributed embedded system used for control and data capture The resulting data is stored in the database Any authorised user can have access to the data, searchable and manipulated as
User Interface Software
The code called by the user is in the form of CGI programs The CGI code can be written to process user requests into queries for the database and return the data in the form that the user requires
Data Collection and Control
The code for this part of the task is now totally separate and can be written using the most appropriate programming techniques The embedded system is often distributed and may use devices as the Netiom as part of the control and data collection methods used
Conclusions
The integration of web access with embedded systems takes many forms and is a growth area at the moment This trend is helped by the increasing complexity of embedded devices, such as micro-controllers, made posible by advances in semiconductor technologies
Hardware Review: Memory types
DRAM
This type of memory is used when a large amount of storage is required at low cost. The storage element is a capacitor which can be either charged or not charged. The main problem is that the charge leaks away and has to be replaced before the data is lost. This feature is reflected in the full name of Dynamic Ram. The complexity of the circuitry needed to refresh the data does reduce the cost advantage of the low number of transistors required per bit.
Video RAM
This device is derived from the DRAM A DRAM used as a conventional memory as well as additional hardware to use the data at the same time for the Video display Essentially the hardware consisted of a shift register which converted the parallel data to serial to be clocked out to drive the video display
SRAM
The full name of this device is Static RAM The data is held without refreshing all the time the power is applied The cost per bit is much higher than for DRAM as more transistors are involved in the circuit for each bit The circuit can be designed for low power operation despite the extra devices per bit as the power consumption is low except when switching
FLASH MEMORY
This is non volatile storage, i.e. the data is not lost when the power is removed The circuit uses a single transistor as a storage cell Write operation can take up to several milliseconds, but reads can be as low as 70 to 100 nanoseconds This specification makes it a suitable device for program storage
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