PCD6003 Ver la hoja de datos (PDF) - Philips Electronics
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PCD6003 Datasheet PDF : 96 Pages
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Philips Semiconductors
Digital telephone answering machine chip
Product specification
PCD6003
10.5 Interface to DSP
The DSP to Microcontroller Interface (DMI) can be used for
the following purposes:
• Transferring compressed speech data from
microcontroller to DSP
• Transferring compressed speech data from DSP to
microcontroller
• Transferring DSP parameters (DSP mode, tone
frequency etc.) from microcontroller (API) to the DSP
• Transferring DSP events (Caller ID, Ring Detect, VOX,
Call Progress etc.) to the microcontroller.
The microcontroller and the DSP can communicate by
means of 6 SFRs (MTD0, MTD1 and MTD2 and DTM0,
DTM1 and DTM2) and 4 DSP I/O registers (DTMC,
DTMD, MTDC and MTDD), see Fig.11. The DTMC and
MTDC registers are used for communication and control
and the DTMD and MTDD registers for transferring data.
The Micro Transmit (MT), DR (DSP receive) and DT (DSP
Transmit), Micro Receive (MR) ensure that either the old
data is read or new data is read although the DSP and
microcontroller operate on different clocks. This can be
achieved by means of simple handshake circuitry in either
direction. The DR state machine ensures that the DSP will
never read new MTDC control data and old MTDD speech
data. In order to guarantee proper transitions of the
DR state machine the DSP always has to read the DTMC
first and afterwards the DTMD IO register.
The TICB generates the DSP_event interrupt when it
receives a dsp_uc_req signal. The dsp_uc_req cannot be
generated by the microcontroller because the dsp_event
interrupt must be able to wake-up the microcontroller from
Power-down.
MTD0/1/2 are written by the microcontroller. After each
write to MTD0 the contents of MTD0/1/2 are transferred to
the 16-bit register MTDD and the 8-bit register MTDC (the
MSB is set to 00H), which can be read by the DSP via the
DSP I/O bus. In this way the DSP always receives a valid
control byte and a valid 16-bit data word. If MTD0 is written
while the DSP is turned off the MTD0 value will be
transferred to the MTDC IO-register as soon as the DSP is
turned on.
The MTDC and MTDD registers are continuously and
immediately read by the DSP after every FS1 interrupt.
The microcontroller can write a new word to MTD0/1/2 but
has to wait for at least 125 µs to be sure that the DSP has
read the previous value.
DTM0/1/2 are read by the microcontroller as SFRs. The
contents of the DTMD and DTMC registers are transferred
to the DTM0/1/2 SFRs when the DSP writes the DTMC
register. At this time an interrupt signal called DSP_event
is generated to the microcontroller, which triggers the
microcontroller to read the DTM0/1/2 SFRs. In this way
DSP events and speech data can be transferred easily to
the microcontroller. The DSP will transfer a maximum of
3 bytes, one command byte and two data bytes, for
example; every 125 µs to the microcontroller. Thus one
write to DTMC takes place every 125 µs.
Similarly, the microcontroller can transfer a maximum of
3 bytes every 125 µs to the DSP. Thus one write to MTD0
takes place every 125 µs. The default rate for the
FS_event interrupt will be FS1/8 resulting in a data transfer
rate of 10 words every 10 ms which equals 16 kbits/s.
In case a higher rate is needed the FS_event interrupt rate
can be switched to FS1/4.
10.6 Interface to Real-Time Clock (RTC)
When the RTC_event interrupt is enabled in IEN1 and the
‘global enable’ bit in IEN0 is set and the PCD6003 is not in
Emergency mode (CKCON.7 = 1), the microcontroller will
get an RTC_event interrupt every 1 minute. The RTC
interrupt service routine must clear the RTC flag. The
RTC_event interrupt will also wake-up the microcontroller
when it is in the Power-down or in the Idle state. Under
power saving conditions this will allow the user to switch off
the microcontroller and still maintain an accurate real time
clock.
2001 Apr 17
30
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