dsPICDEM™ 1.1 Plus Development Board User’s Guide
DS70099D-page 36
©
2006 Microchip Technology Inc.
• Data Converter Interface – Interfaced to an external Si3000 voice band Codec for
transmission of DTMF PCM signals
• INTx pins – Used for detecting switch SW1-SW4 inputs
• Hierarchical/Prioritized Interrupt Control with nesting enabled
3.4
DATA AND CONTROL FLOW
3.4.1
Power-up Sequence
The power-up peripheral initialization sequence is shown in Table 3-3.
TABLE 3-3:
POWER-UP PERIPHERAL INITIALIZATION SEQUENCE
Seq
Module or Function
Initialization Process
1
Timer1
Configured to count to 125 µS, but not enabled.
2
Timer2
Configured to count to 1 second using a 256:1 prescaler
setting.
3
Timer3
Configured to count up to 1.14 seconds using the 256:1
prescaler setting.
4
Timer4 and Timer5
Configured to operate in the 32-bit Timer mode, but not
enabled until needed.
5
Interrupt Service
Routine (ISR)
Processing is enabled for Timer2 and Timer3.
6
UART2
Both the transmitter and receiver are configured for
interrupt-driven operation at 57600 baud.
7
SPI 2
Initially configured to operate in an interrupt-driven mode at
F
CY
/8 Hz (where F
CY
= 7.3728 MHz). The module communi-
cates at F
CY
/8 Hz in 8-bit mode while displaying results on the
LCD controller. When it is used to step the MCP41010, it
operates in the 16-bit mode at F
CY
/32 Hz.
8
Data Converter
Interface (DCI)
Configured for Master mode. Initially configured to use two of
four buffers. Transmits/receives in time slot 1 at the frame rate
of 7200 Hz for configuring the Si3000 external voice band
Codec.
9
Si3000
Configured for Slave mode. The Si3000 line and speaker
ports are enabled. Signal attenuation is set to 0 dB. The ADC
input from the Si3000 is attenuated by 34.5 dB and is not used
in this demo.
10
DCI
Re-initialized to operate with all four buffers in interrupt-driven
mode for transmitting DTMF PCM words to the Si3000 Codec.
11
External interrupt
pins INT1-INT4
Configured to interrupt on the falling edge and used for
switches SW1-SW4, respectively.
12
12-bit ADC
Configured to operate at 16000 Hz sampling rate and gener-
ate an interrupt every 16 sample-convert sequences. The
ADC samples channel AN3 (sine wave), AN4 (RP2), AN5
(RP3), AN6 (RP1) and AN8 (temperature sensor U9).
13
Interrupts
Peripheral interrupts are configured. Nested interrupts are
enabled.
