ISD-T360 ETC [List of Unclassifed Manufacturers], ISD-T360 Datasheet - Page 45

• Manufacturer Part Number: ISD-T360
• Description: VoiceDSP Digital Speech Processor with Master/Slave, Full-Duplex Speakerphone, Multiple Flash and ARAM/DRAM Support
• Manufacturer: ETC [List of Unclassifed Manufacturers]

2—SOFTWARE
2.1.7
The PDM (Go To Power-Down Mode) command
switches the ISD-T360SB to power-down mode.
The purpose of the PDM command is to save
power during buttery operation, or for any other
power saving cause. During power-down mode
only basic functions, such as ARAM/DRAM re-
fresh and time and date update, are active (for
more details refer to POWER-DOWN MODE de-
scription on page 1-4).
This PDM command may only be issued when
the processor is in the IDLE mode (for an expla-
nation of the ISD-T360SB states, see “Command
Execution” on page 2–2). If it is necessary to
switch to power-down mode from any other
state, the controller must first issue a S (Stop)
command to switch the processor to the IDLE
state, and then issue the PDM command. Send-
ing any command while in power-down mode
resets the VoiceDSP processor detectors, and re-
turns it to normal operation mode.
NOTE
2.2
This section provides details of the peripherals in-
terface support functions and their principle op-
eration. It is divided into the following subjects:
• Microcontroller Interface (Slave
• Memory Interface
• Codec Interface
ISD
MICROWIRE)
Entering or exiting power-down mode can
distort the real-time clock by up to 500 µs.
Thus, to maintain the accuracy of the real-
time clock, enter or exit the power-down
mode as infrequently as possible.
POWER-DOWN MODE
PERIPHERALS
2.2.1
MICROWIRE/PLUS™ is a synchronous serial com-
munication protocol minimizes the number of
connections, and thus the cost, of communicat-
ing with peripherals.
The VoiceDSP MICROWIRE interface implements
the MICROWIRE/PLUS interface in slave mode,
with an additional ready signal. It enables a mi-
crocontroller to interface efficiently with the
VoiceDSP processor application.
The microcontroller is the protocol master and
provides the clock for the protocol. The VoiceD-
SP processor supports clock rates of up to 400
KHz. This transfer rate refers to the bit transfer; the
actual throughput is slower due to byte process-
ing by the VoiceDSP processor and the micro-
controller.
Communication is handled in bursts of eight bits
(one byte). In each burst the VoiceDSP proces-
sor is able to receive and transmit eight bits of
data. After eight bits have been transferred, an
internal interrupt is issued for the VoiceDSP pro-
cessor to process the byte, or to prepare another
byte for sending. In parallel, the VoiceDSP pro-
cessor sets MWRDY to 1, to signal the microcon-
troller that it is busy with the byte processing.
Another byte can be transferred only when the
MWRDY signal is cleared to 0 by the VoiceDSP
processor. When the VoiceDSP processor trans-
mits data, it expects to receive the value 0xAA
before each transmitted byte. The VoiceDSP
processor reports any status change by clearing
the MWRQST signal to 0.
If processor command’s parameter is larger than
one byte, the microcontroller transmits the Most
Significant Byte (MSB) first. If a return value is larg-
er than one byte, the VoiceDSP processor trans-
mits the MSB first.
The following signals are used for the interface
protocol. Input and output are relative to the
VoiceDSP processor.
MICROCONTROLLER INTERFACE
2-5