CS49310 datasheet(48/86 Pages) CIRRUS

48 / 86 page

CS49300 Family DSP

DS339PP4

host can safely read a byte from the Host

Message Register (A[1:0] = 00b).

5) If the host expects to read any more response

bytes, the host should once again check the

HOUTRDY bit (return to step 1). Please refer

to one of the application code user’s guides to

determine the length of messages to read from

the CS493XX. Typically this length is 1, 3 or 6

bytes, and can be deduced from the message

OPCODE.

6) After the response has been read the host

should wait at least 100 uS and check

HOUTRDY one final time. If HOUTRDY is

high once again this means that an unsolicited

message has come during the read process and

the host has another message to read (i.e. skip

back to step 4 and read out the new message).

EXTERNAL MEMORY

If using one of the serial modes, i.e. SPI or I2C, the

system designer has the option of using external

memory. The external memory interface is not

compatible with the parallel modes since there are

shared pins that are needed by each mode.

The external memory interface was designed for

autoboot and to extend the data memory range of

the DSP during runtime. The application user’s

guide for a particular code load will inform the

system designer if memory is required. If no

mention is made of external memory, then external

memory is not required for that application.

The external memory interface is implemented on

the

CS493XX

with

the

following

signals:

EMAD[7:0], EXTMEM, EMOE, and EMWR.

Table 8 shows the pin name, pin description and

pin number of each signal on the CS493XX.

EMAD[7:0] serve as a multiplexed address and

data bus. EMOE is an active-low external-memory

data output enable as well as the address latch

strobe. EMWR is an active low write enable.

Figure 29. Typical Parallel Host Mode Control Read

Sequence Flow Diagram

READ_BYTE_*(HOST CONTROL REGISTER)

READ_BYTE_*(HOST MESSAGE REGISTER)

MORE BYTES

HOUTRDY==1

YES

TO READ?

YES

FINISHED

INTREQ = 0

YES

WAIT 100 uS

READ_BYTE_*(HOST CONTROL REGISTER)

HOUTRDY==1

YES

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