CS493112-CL View Datasheet(PDF) - Cirrus Logic

Part Name

Description

MFG CO.

CS493112-CL

Multi-Standard Audio Decoder Family

Cirrus Logic 

CS49300 Family DSP

8.3. Decreasing Autoboot Times Using

GFABT Codes (Fast Autoboot)

Instead the host toggling the RESET line while

ABOOT is held low, the host decrease the

Autoboot download time by instead downloading a

special code called “GFABT” (Genesis Fast

Autoboot) which first speeds up the DSP’s core

clock, and then automatically causes the DSP to

Autoboot itself from external ROM.

Basically, the host should perform a normal serial

host boot with one of the GFABT codes (gfabt8.ld,

gfabt6.ld or gfabt4.ld) as described in Section

8.1.1, (with ABOOT held high). Immediately

following the download of the GFABT code, the

DSP will start to act the exact same way as if the

host had toggled the RESET line with ABOOT held

low, only now, the code image held in the external

flash or eprom page will now be downloaded

anywhere from 1.5 to 3 times faster than using

Autoboot, depending on the gfabt code that was

first downloaded.

The normal DSP clock divide factor during

Autoboot is 12 (VCO open loop frequency divider).

The gfabt8.ld code changes that divide factor to 8,

the gfabt6.ld code changes it to 6, and the gfabt4.ld

code changes it to 4. Contact your FAE in order to

obtain these gfabt codes.

Some sample data for various autoboot times can

be seen below in Table 11 using the

ac3_pl2_reeq_493264_08.ld application code. It

shows that the autoboot times after downloading

gfabt8.ld, gfabt6.ld, and gfabt4.ld are

approximately 1.5, 2, and 3 times faster than a

standard autoboot. The typical autoboot time

listed in the datasheet of 200 ms will therefore

become 135 ms (200ms/1.5), 100ms (200ms/2),

and 70ms (200/3) with gfabt8, 6, and 4,

respectively.

Application

Code Name

(8.3 File Name)

Application

Code Name

(Long File

Name)

Code Size on

Disk

Open Loop

VCO

Standard Autoboot Times

ac3_pl~1.ld

dts_6d~1.ld

eff_49~1.ld

ac3_pl2_

reeq_

493264_

08.ld

94 k

dts_6dot1_

reeq_

493264_

04.ld

94 k

eff_4932xx

_14.ld

47 k

GFABT4.LD

ac3_pl~1.ld

GFABT6.LD

ac3_pl~1.ld

GFABT8.LD

ac3_pl~1.ld

Code Size in

Bytes

Sample 1

Sample 2

Sample 3

12.5 MHz

12.4 MHz

11.7 MHz

24 k

98 ms

99 ms

97 ms

24 k

96 ms

98 ms

96 ms

12 k

48 ms

50 ms

48 ms

34 ms

34 ms

32 ms

50 ms

50 ms

50 ms

65 ms

67 ms

66 ms

Table 11. Reduced Autoboot Times using GFABT8.LD, GFABT6.LD, and GFABT4.LD on a CS493264-CL

Rev. G DSP

DS339F7

61

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