Hardware Reference
In-Depth Information
14 Additional Design Examples
This chapter presents three additional FSM-based designs. They are included in a sepa-
rate chapter because theoretical details and background material are also provided,
leading to much longer design examples. Moreover, FSMs from all three categories are
involved, depending on the application. The chapter starts with a simple LCD driver,
followed by the I
2
C and SPI interfaces, which are currently the most popular circuits
for serial communication between integrated circuits.
14.1 LCD Driver
Like SSDs (seven segment displays), alphanumeric LCDs (liquid crystal displays) are
popular options for displaying readings in all sorts of equipment, from watches to car
speedometers, from microwave ovens to medical instruments. Their main advantages
over SSDs are a much lower power consumption and the possibility of displaying
basically any character and also simple i gures, but at a higher price and a more
complex driver.
14.1.1 Alphanumeric LCD
A popular alphanumeric LCD is shown in i gure 14.1, which contains two lines of 16
characters each. A picture of the display is shown in i gure 14.1a. The corresponding
pinout is exhibited in i gure 14.1b. The internal display layout is illustrated in i gure
14.1c, showing 16
5 each. In i gure 14.1d, its most frequent
exhibition mode is depicted, consisting of 8
×
2 dot arrays of size 8
×
5 characters. Finally,
in i gure 14.1e, its other predei ned exhibition mode is depicted, consisting of 11
×
5-dot arrays for 7
×
×
5-
dot arrays, for 10
5 characters.
Even though this kind of display can also be found with I
2
C and other serial inter-
faces, for low-cost applications the use of parallel access through an HD44780U micro-
controller constitutes the industry standard. Such a controller (from Hitachi, or an
equivalent one such as KS0066U from Samsung) is installed on the back of the device,
acting as the interface between the LCD and the external world. The device is then
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