Cirrus Logic CS4351 - Manual (Page 15)

DS566F1 15
CS4351
4. APPLICATIONS
4.1 Sample Rate Range/Operational Mode Detect
The device operates in one of three operational modes. The allowed sample rate range in each mode will
depend on whether the Auto-Detect Defeat bit is enabled/disabled.
4.1.1 Auto-Detect Enabled
The Auto-Detect feature is enabled by default. In this state, the CS4351 will auto-detect the correct mode
when the input sample rate (F
s
), defined by the LRCK frequency, falls within one of the ranges illustrated
in Table 1 . Sample rates outside the specified range for each mode are not supported.
4.1.2 Auto-Detect Disabled
The Auto-Detect feature can be defeated only by the format bits in the control port register 02h. In this
state, the CS4351 will not auto-detect the correct mode based on the input sample rate (F
s
). The opera-
tional mode must then be set manually according to one of the ranges illustrated in Table 2 . Please refer
to Section 6.2.3 for implementation details. Sample rates outside the specified range for each mode are
not supported. In stand-alone mode it is not possible to disable auto-detect of sample rates.
4.2 System Clocking
The device requires external generation of the master (MCLK), left/right (LRCK) and serial (SCLK) clocks.
The left/right clock, defined also as the input sample rate (F
s
), must be synchronously derived from the
MCLK according to specified ratios. The specified ratios of MCLK to LRCK, along with several standard au-
dio sample rates and the required MCLK frequency, are illustrated in
Tables 3 through 5 .
Refer to Section 4.3 for the required SCLK timing associated with the selected Digital Interface Format and
to the “Switching Specifications - Serial Audio Interface” section on page 10 for the maximum allowed clock
frequencies.
Input Sample Rate (F
S
) MODE
4 kHz - 50 kHz Single-Speed Mode
84 kHz - 100 kHz Double-Speed Mode
170 kHz - 200 kHz Quad-Speed Mode
Table 1. CS4351 Auto-Detect
FM1 FM0 Input Sample Rate (F
S
) MODE
0 0 Auto speed mode detect Auto
0 1 4 kHz - 50 kHz Single-Speed Mode
1 0 50 kHz - 100 kHz Double-Speed Mode
1 1 100 kHz - 200 kHz Quad-Speed Mode
Table 2. CS4351 Mode Select