NSAM265SR Datasheet, PDF (6/58 Pages) National Semiconductor (TI) – CompactSPEECH Digital Speech Processors

1 0 Theory of Operation (Continued)
TABLE 1-1 CompactSPEECH States and Transitions (Continued)
Command
Description
Source State
Message Management Commands
CMT
Cut Message Tail
IDLE
DM
Delete Message
IDLE
DMS
Delete Messages
IDLE
GL
Get Length
IDLE
GMT
Get Message Tag
IDLE
GNM
Get Number of Messages
IDLE
GTM
Get Tagged Message
IDLE
RRAM
Read RAM
IDLE MEMORY READ
SMT
Set Message Tag
IDLE
WRAM
Write RAM
IDLE MEMORY WRITE
Result State
IDLE
IDLE
IDLE
IDLE
IDLE
IDLE
IDLE
MEMORY READ
IDLE
MEMORY WRITE
Command is valid in IDLE state but has no effect
1 3 COMMAND EXECUTION
A CompactSPEECH command is represented by an 8-bit
opcode Some commands have parameters and some
have a return value Commands are either synchronous or
asynchronous
Synchronous Commands
A synchronous command completes execution before the
microcontroller can send a new command (e g GMS
GEW)
A command sequence starts when the microcontroller
sends an 8-bit opcode to the CompactSPEECH followed by
the command’s parameters (if any)
The CompactSPEECH executes the command and if re-
quired transmits a return value to the microcontroller Upon
completion the CompactSPEECH notifies the microcontrol-
ler that it is ready to accept a new command
Asynchronous Commands
An asynchronous command starts execution in the back-
ground and notifies the microcontroller which can send
more commands while the current command is still running
(e g R P)
The Status Word
The CompactSPEECH processor has a 16-bit status word
to indicate events that occur during normal operation The
CompactSPEECH activates the MWRQST signal to indi-
cate a change in the status word This signal remains active
until the CompactSPEECH receives a GSW command
The Error Word
The 16-bit error word indicates errors that occurred during
execution of the last command If an error is detected the
command is not processed the EV ERROR bit in the
status word is set to 1 and the MWRQST signal is activat-
ed
Error Handling
When the microcontroller detects that the MWRQST signal
is active it should issue the GSW (Get Status Word) com-
mand which deactivates the MWRQST signal Then it
should test the EV ERROR bit In the status word and
if it is set send the GEW (Get Error Word) command to read
the error word for details of the error
For a detailed description of each of the CompactSPEECH
commands see Section 3 0
1 4 TUNABLE PARAMETERS
The CompactSPEECH processor can be adjusted to your
system’s requirements For this purpose the Compact-
SPEECH supports a set of tunable parameters which are
set to their default values after reset and can be later modi-
fied with the TUNE command By tuning these parameters
you can control various aspects of the CompactSPEECH’s
operation such as silence compression tone detection no-
energy detection etc
Table 3-1 describes all the tunable parameters in detail
Section 3 describes the TUNE command
1 5 MESSAGES
The CompactSPEECH message manager supports a wide
range of applications which require different levels of DAM
functionality
The message-organization scheme and the message tag
support advanced memory-organization features such as
multiple OutGoing Messages (OGMs) mailboxes and the
ability to distinguish between InComing Messages (ICMs)
and OGMs
The NSAM265SF can store up to 256 messages per 4 Mbits
of AFLASH storage The NSAM265SR can store up to 100
messages per 4 Mbits of ARAM storage
A message is the basic unit on which most of the Compact-
SPEECH commands operate A CompactSPEECH mes-
sage stored in ARAM or AFLASH can be regarded as a
computer file stored on a mass-storage device
A message is created with either the R or the WRAM (Write
RAM) command When a message is created it is assigned
a time-and-day stamp and a message tag which can be
read by the microcontroller
The R command takes voice samples from the codec com-
presses them and stores them in the message memory
6