CS49310 datasheet(63/90 Pages) CIRRUS

63 / 90 page

CS49300 Family DSP

DS339F7

8.3.1. Design Considerations when

using GFABT Codes

The designer should be aware that the gfabt codes

do not lock the PLL, so therefore the actual time

involved with autobooting is subject to the open

loop VCO frequency. The PLL is only locked when

the command is sent from the host, typically along

with the kickstart command. Also, the designer

should take into account the access time of the

Flash Memory, EPROM, and latches used in their

specific design. While there is a temptation to use

the gfabt4 code which would theoretically minimize

the Autoboot time, the designer should realize that

this may result in the DSP to attempting to

Autoboot too quickly, resulting in clocking times

that exceed that of the specified access times of

particular

external

memory

devices

the

associated latches.

The designer should note that the times listed in

Table 11 were taken from 3 sample CS493264-CL

Rev. G devices and are in no way a guarantee of

the times that your design will achieve as all values

are dependent on the open loop frequency of the

DSP. Furthermore the times listed in Table 11 DO

NOT include the code initialization time (the time

spent after download while the code prepares for

messages). Therefore, the times listed above

should be used as the upper bound on boot time

when using the gfabt codes.

8.4. Internal Boot

Certain applications are stored in the ROM of the

CS493253,

CS493254,

CS493263

and

CS493264. To enable these applications a special

loader called an internal boot assist program must

be used. This internal boot assist (or IBA) code can

be downloaded using either host boot or autoboot

methods. After the IBA program has been

downloaded, it enables the internally stored

application code. The IBA codes are typically

around 350 bytes in size and hence can easily be

stored in a host controller.

8.5. Application Failure Boot Message

Each piece of application code is specifically

tailored for an individual part in the CS493XX

family. Although it is possible to load a piece of

code

into

the

wrong

chip

and

receive

BOOT_SUCCESS byte, the code will not initialize

itself. In order to facilitate the debug of designs

which can accept many members of the CS493XX

family, an APPLICATION_FAILURE message is

provided.

As mentioned earlier, the host must wait for at least

5ms after download before sending configuration

messages to the CS493XX. This provides time for

the code to initialize itself. If the INTREQ pin is low

after the download process has completed, the

host should read from the CS493XX. The byte

0xF0 indicates APPLICATION_FAILURE. This

byte informs the host that the application code was

loaded into an incompatible DSP.

Although most of the messages listed in Tables 9

and 10 are essentially ignored for autoboot, it

should be noted that the APPLICATION_FAILURE

message is applicable whether host boot or

autoboot is used.

8.6. Resetting the CS493XX

Resetting the CS493XX uses a combination of

software and hardware. To reset the device, a

previous application must have been downloaded.

The flow diagram in Figure 39, "Performing a

Reset" on page 64 shows the procedure for

performing a reset.

The following is a detailed description of a reset

sequence to the CS493XX. All writes and reads

with the CS493XX should follow the protocol given

in Section 6, “Control” on page 36.

1) Reset begins when the host issues a hard reset

and holds the mode pins appropriately (WR,

RD, and PSEL) as described in Section 6,

“Control” on page 36. It is assumed that the

communication

protocol

followed

for

whichever communication mode is chosen by

the host.

2) The host should then send the message

SOFT_RESET (0x000001). This will reset the

previously downloaded application with all of

the hardware configurations in their default

states. The application code user’s guide for

each application lists those parameters which

are affected by a SOFT_RESET.

3) After waiting 5 ms to allow the downloaded

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