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參數(shù)資料
| 型號(hào)： | NSAM265SRA |
| 廠商： | National Semiconductor Corporation |
| 英文描述： | CompactSPEECH Digital Speech Processors |
| 中文描述： | CompactSPEECH數(shù)字語音處理器 |
| 文件頁數(shù)： | 12/58頁 |
| 文件大?。?/td> | 712K |
| 代理商： | NSAM265SRA |
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2.0 Functional Description
(Continued)
TL/EE/12378–4
FIGURE 2-1. Recommended Power-On Reset Circuit
2.3 THE SERIAL MICROWIRE INTERFACE
The CompactSPEECH supports the MICROWIRE synchro-
nous serial communication protocol. The communication
protocol used by the CompactSPEECH is an extension of
this protocol scheme. The microcontroller is the protocol
master and provides the clock for the protocol. The Com-
pactSPEECH supports clock rates of up to 400 kHz. This
transfer rate refers to the bit transfer; the actual throughput
is slower due to byte processing by the CompactSPEECH
and the microcontroller.
Communication is handled in bursts of eight bits (one byte).
In each burst the CompactSPEECH is able to receive and
transmit eight bits of data. After eight bits have been trans-
ferred, an internal interrupt is issued for the Compact-
SPEECH to process the byte, or to prepare another byte for
sending. In parallel the CompactSPEECH sets (1) the
MWRDY signal to signal the microcontroller that it is busy
with the byte processing. Another byte can be transferred
only when the MWRDY signal is asserted (0) by the Com-
pactSPEECH. When the CompactSPEECH transmits data, it
expects to receive the value 0xAA as an echo after each
transmitted byte. The CompactSPEECH reports any status
change by asserting the MWRQST signal (0).
If a parameter of a CompactSPEECH command is bigger
than one byte, the Most Significant Byte (MSB) should be
transmitted first by the microcontroller. If a return value is
bigger than one byte, the MSB is transmitted first by Com-
pactSPEECH.
Note:
Although the CompactSPEECH does not enforce a lower limit on the
bit transfer rate, the time between bytes within the same command
must not exceed 2 ms.
2.3.1 Signal Description
The following signals are used for the interface protocol.
Input and output are relative to the CompactSPEECH.
Input Signals
MWDIN
MICROWIRE Data In. Used for input only, for transferring
data from the host to the CompactSPEECH.
MWCLK
This signal serves as the synchronization clock during com-
munication. One bit of data is transferred on every clock
cycle. The input data is available on MWDIN, and is latched
on the clock rising edge. The transmitted data is output on
MWDOUT on the clock falling edge. The signal should re-
main low when switching MWCS.
MWCS
MICROWIRE Chip Select. The MWCS signal is asserted (0)
to indicate that the CompactSPEECH is accessed. Assert-
ing the MWCS causes the CompactSPEECH to start driving
the MWDOUT with bit 7 of the transmitted value. Negating
the signal resets the transfer-bit counter of the protocol, so
it can be used as a synchronization between the Compact-
SPEECH and the microcontroller.
To prevent false detection of access to the Compact-
SPEECH due to spikes on the MWCLK signal, use this chip
select signal, and toggle the MWCLK input signal, only
when the CompactSPEECH is accessed.
Output Signals
MWDOUT
MICROWIRE Data Out. Used for output only, for transferring
data from the CompactSPEECH to the microcontroller.
When the CompactSPEECH receives data it is echoed back
to the microcontroller on this signal, unless the received
data is 0xAA. In this case, the CompactSPEECH echoes a
command’s return value.
MWRDY
MICROWIRE Ready. When active (0), this signal indicates
that the CompactSPEECH is ready to transfer (receive or
transmit) another byte of data. This signal is deactivated (1)
by the CompactSPEECH upon each byte transfer comple-
tion. It remains deactivated, while the CompactSPEECH is
busy reading the byte, writing the next byte or executing the
received command (after the last parameter has been re-
ceived). MWRDY is asserted by reset.
For proper operation after a hardware reset, this signal
should be pulled up.
MWRQST
MICROWIRE Request. When active (0), this signal indicates
that new status information is available. MWRQST is deacti-
vated (1), after the CompactSPEECH receives a GSW (Get
Status Word) command from the microcontroller. After re-
set, this signal is active (0) to indicate that a reset occurred.
MWRQST, unlike all the signals of the communication pro-
tocol, is an asynchronous line that is controlled by the Com-
pactSPEECH firmware.
2.3.2 Signal Use in the Interface Protocol
After reset, the MWRQST signal is activated (0) and the
MWRDY signal is activated (0).
The MWRQST signal is activated to indicate that a reset
occurred. The EVDRESET bit in the status register is used
to indicate a reset condition.
The GSW command should be issued after reset to verify
that the EVDRESET event occurred and to deactivate the
MWRQST signal.
While the MWCS signal is active (0), the CompactSPEECH
reads data from MWDIN on every rising edge of MWCLK.
CompactSPEECH also writes every bit back to MWDOUT.
This bit is either the same bit which was read from MWDIN
(in this case it is written back as a synchronization echo
mechanism after some propagation delay), or it is a bit of a
value the CompactSPEECH transmits to the microcontroller
(in this case it is written on every falling edge of the clock).
When a command has more than one parameter/return-val-
ue, the parameters/return-values are transmitted in the or-
der of appearance. If a parameter/return-value is more than
one byte long, the bytes are transmitted from the most sig-
nificant to the least significant one.
12
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