Hi everybody. I'm finishing my RM9200 board (32MB SDRAM, 2MB SPI NOR, Smart Media, RTL8201). Now I need to choose te audio interface. First - I was thinking about AC97 codec - like National's LM4549 because I saw this chip in some RM9000 SDK boards. But I saw some posts with information that AT91RM9200 and its SSC doesn't work with AC97 codec. Can somebody confirm (or better not ;) ) this fact ? So... AT91RM9200 and audio interface - only one solution it is i2s codec ? Am I right ?
Best regards
The AC-97 runs at 20 MHz+ and this speed is not supported by the AT91RM9200. Think it tops out at MCK/4 = 15 Mhz. Later chips have faster SSCs. Also you need to run several timeslots, which is difficult to implement even if you support the high speed. The AC-97 peripheral used in the AVR32 AP7000 is now available for use in future AT91 chips.
The I2S based AT73C213 Audio DAC has been used with the AT91SAM9261.
The AT91RM9200 datasheet says MCK max is 80 MHz
Yes, but the CPU PLL tops out at 180 MHz.
180 MHz/2 = 90 MHz, so this is illegal. 180 MHz/3 = 60 MHz and 60 Mhz / 4 = 15.You can do PLL = 160 MHz and get MCLK = 80 MHz.
80 MHz / 4 = 20 MHz, but the real AC-97 clock is around 24 MHz IIRC.
Ok guys. Thanks for this explanation. Now everything is clear. I have decided to choose something from TI family TLV320AIC2x
Best regards
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