Programmable Timers
10-6
Am186™CC/CH/CU Microcontrollers User’s Manual
TxCMPA value is reached (timer is now comparing against TxCMPB). The RIU bit is 0 when
the TxCMPB value is reached (timer is now comparing against TxCMPA).
10.5.5
Software Polling
Software can poll the MC bit in the T0CON, T1CON, and T2CON registers to monitor timer
status rather than using interrupts. This bit must be cleared by software.
10.5.6
Generating Waveforms
When programmed to use both compare values (ALT bit in TxCON is 1), Timer 0 and Timer
1 can generate waveforms on the associated TMROUT pin. The TxCMPA value determines
the duration of the High phase of the output waveform. The TxCMPB value determines the
duration of the Low phase of the output waveform. For more information, see the timer
examples available on the AMD website at ftp.amd.com.
10.5.7
Pulse Width Demodulation
For many applications, such as bar-code reading, it is necessary to measure the width of
a signal in both its High and Low phases. The Am186CC/CH/CU microcontrollers provide
a pulse width demodulation (PWD) option to fulfill this need. The PWD bit in the System
Configuration (SYSCON) register enables the PWD option. Note that the Am186CC/CH/
CU microcontrollers do not support analog-to-digital conversion.
Figure 10-1 on page 10-1 shows the routing of signals when pulse width demodulation is
either enabled or disabled. The waveform for PWD mode is input on the INT8/PWD pin.
This pin is of type Schmitt trigger in both normal interrupt and PWD modes. Note that this
pin is multiplexed with PIO6 and defaults to the PIO function at external and internal reset.
In PWD mode, software uses Timer 0 and Timer 1 to measure the High and Low pulse
width of the input signal. Interrupt 8 (Channel 13, type 1dh) and interrupt 7 (Channel 12,
type 1ch) notify software of the transitions of the measured input signal.
Timer 0 starts its count on the Low-to-High transition on the PWD input and counts the High
signal duration. Timer 1 starts its count on the High-to-Low transition on the PWD input
and counts the Low signal duration. The Low-to-High transition of the PWD input generates
an interrupt request using Channel 13 (type 1dh). The High-to-Low transition of the PWD
input generates an interrupt request using Channel 12 (type 1ch).
Figure 10-2 shows the behavior of the PWD function for a typical input waveform.
Figure 10-2
Pulse Width Demodulation Example
(1)
(3)
(1)
(3)
(2)
(2)
(4)
(4)
1. A Channel 13 (INT8) interrupt request is generated.
2. Timer 0 counts during the high phase of the input signal.
3. A Channel 12 (INT7) interrupt request is generated.
4. Timer 1 counts during the low phase of the input signal.
Summary of Contents for Am186 CC
Page 1: ...Am186 CC CH CU Microcontrollers User s Manual Order 21914B...
Page 4: ...iv Am186 CC CH CU Microcontrollers User s Manual...
Page 18: ...Table of Contents xviii Am186 CC CH CU Microcontrollers User s Manual...
Page 24: ...Introduction xxiv Am186 CC CH CU Microcontrollers User s Manual...
Page 40: ...Architectural Overview 1 16 Am186 CC CH CU Microcontrollers User s Manual...
Page 86: ...System Overview 3 36 Am186 CC CH CU Microcontrollers User s Manual...
Page 92: ...Emulator Support 4 6 Am186 CC CH CU Microcontrollers User s Manual...
Page 112: ...DRAM Controller 6 8 Am186 CC CH CU Microcontrollers User s Manual...
Page 134: ...Interrupts 7 22 Am186 CC CH CU Microcontrollers User s Manual...
Page 186: ...Programmable I O Signals 9 8 Am186 CC CH CU Microcontrollers User s Manual...
Page 200: ...Watchdog Timer 11 6 Am186 CC CH CU Microcontrollers User s Manual...
Page 232: ...Asynchronous Serial Ports UARTs 13 24 Am186 CC CH CU Microcontrollers User s Manual...
Page 242: ...Synchronous Serial Port SSI 14 10 Am186 CC CH CU Microcontrollers User s Manual...
Page 264: ...High Level Data Link Control HDLC 15 22 Am186 CC CH CU Microcontrollers User s Manual...
Page 332: ...Universal Serial Bus USB 18 34 Am186 CC CH CU Microcontrollers User s Manual...
Page 348: ...Register Summary A 16 Am186 CC CH CU Microcontrollers User s Manual...
Page 376: ...Index Index 18 Am186 CC CH CU Microcontrollers User s Manual...