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參數(shù)資料
| 型號： | NSAM266SAA |
| 廠商： | National Semiconductor Corporation |
| 元件分類： | FLASH |
| 英文描述： | 4 Mbit Uniform Sector, Serial Flash Memory |
| 中文描述： | 4兆位統(tǒng)一部門，串行閃存 |
| 文件頁數(shù)： | 30/52頁 |
| 文件大?。?/td> | 571K |
| 代理商： | NSAM266SAA |
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2.0 Software
(Continued)
The CompactSPEECH MICROWIRE interface implements
the MICROWIRE/PLUS interface in slave mode, with an ad-
ditional ready signal. It enables a microcontroller to inter-
face efficiently with the CompactSPEECH application.
The microcontroller is the protocol master, and provides the
clock for the protocol. The CompactSPEECH supports
clock rates of up to 400 kHz. This transfer rate refers to the
bit transfer; the actual throughput is slower due to byte pro-
cessing 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 MWRDY to
1, to signal the microcontroller that it is busy with the byte
processing. Another byte can be transferred only when the
MWRDY signal is cleared to 0 by the CompactSPEECH.
When the CompactSPEECH transmits data, it expects to
receive the value 0xAA before each transmitted byte. The
CompactSPEECH reports any status change by clearing the
MWRQST signal to 0.
If a parameter of a CompactSPEECH command is bigger
than one byte, the microcontroller should transmit the Most
Significant Byte (MSB) first. If a return value is bigger than
one byte, the CompactSPEECH transmits the MSB first.
2.12 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 microcontroller 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 cleared to 0
to indicate that the CompactSPEECH is being accessed.
Setting MWCS to 1 causes the CompactSPEECH to start
driving MWDOUT with bit 7 of the transmitted value. Setting
the MWCS signal resets the transfer-bit counter of the pro-
tocol, so the signal can be used to synchronize between the
CompactSPEECH 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 set to 1 by the CompactSPEECH after each
byte transfer has been completed. It remains 1, while the
CompactSPEECH is busy reading the byte, writing the next
byte, or executing the received command (after the last pa-
rameter has been received). MWRDY is cleared to 0 after
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 (set to 1), after the CompactSPEECH receives a GSW
(Get Status Word) command from the microcontroller. After
reset, this signal is active (0) to indicate that a reset oc-
curred. MWRQST, unlike all the signals of the communica-
tion protocol, is an asynchronous line that is controlled by
the CompactSPEECH firmware.
2.12.1 Signal Use in the Interface Protocol
After reset, both MWRQST and MWRDY are cleared to 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
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.
The MWRDY signal is used as follows:
1. Active (0) MWRDY signals the microcontroller that the
last eight bits of data transferred to/from the voice mod-
ule were accepted and processed (see below).
2. The MWRDY signal is deactivated (set to 1 by the
CompactSPEECH) after 8-bits of data were transferred
to/from the CompactSPEECH. The bit is set following the
falling edge of the eighth MWCLK clock-cycle.
3. The MWRDY signal is activated (cleared to 0) by the
CompactSPEECH when it is ready to receive the first pa-
rameter byte (if there are any parameters) and so on till
the last byte of parameters is transferred. An active
MWRDY signal after the last byte of parameters indicates
that the command was parsed and (if possible) executed.
If that command has a return value, the microcontroller
must read the value before issuing a new command.
http://www.national.com
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