Owner's manual

Table Of Contents
DS785UM1 26-1
Copyright 2007 Cirrus Logic
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26
Chapter 26
26Keypad Interface
26.1 Introduction
Note: This chapter applies only to the EP9307, EP9312, and EP9315 processors.
The keypad interface has the following features:
A maximum 8x8 array of normally open, single pole contacts
A back drive feature to minimize capacitance effects
A typical scan count limit of 3 consecutive scans
A maximum mechanical bounce time for a key press of 20 milliseconds
A typical interrupt interval between 24 and 44 milliseconds
A low-power wakeup mode
A three-key reset
If the system does not use a keyboard, the Row[7:0] and Column[7:0] pins can be remapped
to General Purpose Input/Output (GPIO) pins. For details, see Chapter 5, “DeviceCfg” on
page 5-25 and Chapter 28, Table 28-4 on page 28-8.
A block diagram for the key array scanning circuitry is shown in Figure 26-1.
Figure 26-1. Key Array Block Diagram
Precounter
Debounce Counter
Row/Collumn
Counter
Pipeline
Scan
Control
Row Decoder
Column Mux
Temp Key Regs Key Regs
Interrupt
Controller
3 Key Reset Key Detector
Diagnostics
Equal
Compare
Pipeline
Row lines
Column lines
Inactive
Interrrupt
3 Key Reset