NSAM265SF datasheet(13/58 Pages) NSC

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20 Functional Description (Continued)

The MWRDY signal is used as follows

1 An active (0) MWRDY signal signals the microcontroller

that the last eight bits of data transferred tofrom the

CompactSPEECH were accepted and processed (see

below)

2 The MWRDY signal is deactivated (set to 1 by the Com-

pactSPEECH) 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 (by the Compact-

SPEECH) when the CompactSPEECH is ready to receive

the first parameter 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 micro-

controller must read the value before issuing a new com-

mand

4 When a return value is transmitted the MWRDY signal is

deactivated after every byte and activated again when

the CompactSPEECH is ready to send another byte or to

receive a new command

The MWRDY signal is activated (set to 0) after reset and

protocol timeout (See Section 233)

The MWRQST signal is used as follows

1 The MWRQST signal is activated (0) when the status

word is changed

2 The MWRQST signal remains active (0) until the Com-

pactSPEECH receives a GSW command

Figure 2-2 illustrates the sequence of activities during a

MICROWIRE data transfer

233 Interface Protocol Error Handling

Interface Protocol Time-Outs

When the time between two consecutive byte transmis-

sions or bytes reception within the same command or re-

turn value exceeds two milliseconds after the MWRDY sig-

nal is asserted a time-out event occurs and the Compact-

SPEECH responds as follows

1 Sets the error bit in the status word to 1

2 Sets the EV

TIMEOUT bit in the error word to 1

3 Activates the MWRQST signal (sets it to 0)

4 Activates the MWRDY signal (sets it to 0)

5 Waits for a new command (After a time-out occurs the

microcontroller must wait at least four milliseconds before

issuing the next command)

Echo Mechanism

The CompactSPEECH echoes back to the microcontroller

all the bits received by the CompactSPEECH Upon detec-

tion of an error in the echo the microcontroller should stop

the protocol clock which eventually will cause a time-out

error (ie ERR

TIMEOUT bit is set in the error word)

Note

When a command has a return value the CompactSPEECH transmits

bytes of the return value instead of the echo value

When the CompactSPEECH is transmitting a byte it ex-

pects to receive the value 0xAA as an echo Upon detection

of an error the CompactSPEECH activates the MWRQST

signal and sets the ERR

COMM bit in the error word

24 CODEC INTERFACE

The CompactSPEECH provides an on-chip interface to a

serial codec The interface supports codec operation in long

or short-frame formats The format is selected with the CFG

command

The codec interface uses four signalsCDIN CDOUT

CCLK and CFS0

Data is transferred to the codec through the CDOUT pin

Data is read from the codec through the CDIN pin

Data transfer between the CompactSPEECH and the serial

codec starts by the CompactSPEECH asserting (high) the

CFS0 frame sync signal After one clock cycle the Com-

pactSPEECH de-asserts CFS0 data from the Compact-

SPEECH is sent to the codec through CDOUT and simulta-

neously data from the codec is sent to the Compact-

SPEECH through CDIN

TLEE12378 – 5

FIGURE 2-2 Sequence of Activities During a MICROWIRE Byte Transfer

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