SPRUJC6A December 2024 – July 2025 AM2752-Q1 , AM2754-Q1
The CPTS_GENFn output cycle can be adjusted by parts per million or by parts per hour. Writing a non-zero value to CPSW3_CPSW_NU_CPTS_TS_GENF_PPM_LOW_REG_L/ CPSW3_CPSW_NU_CPTS_TS_GENF_PPM_HIGH_REG_L enables PPM operations. The PPM counter continually loads and decrements to zero and then loads again. A single CPTS_RFT_CLK adjustment is made when the PPM counter decrements to zero. The adjustment is up or down depending on the CPSW3_CPSW_NU_CPTS_TS_GENF_CONTROL_REG[0] PPM_DIR bit. When PPM_DIR bit is set a single CPTS_RFT_CLK time is subtracted from the generate function counter which has the effect of increasing the generate function frequency by the PPM amount. When PPM_DIR bit is cleared a single CPTS_RFT_CLK time is added to the generate function counter which has the effect of decreasing the generate function frequency by the PPM amount.
Parts Per Million example:
To adjust for 100 parts
per million the configured value for
GENF_PPM[41-0] (through
CPSW3_CPSW_NU_CPTS_TS_GENF_PPM_LOW_REG_L and
CPSW3_CPSW_NU_CPTS_TS_GENF_PPM_HIGH_REG_L) is:
1,000,000/100 =
10,000(decimal)
Parts Per Hour example:
To adjust for 1 part
per hour at 1 GHz CPTS_RFT_CLK the configured
value for GENF_PPM[41-0] (through
CPSW3_CPSW_NU_CPTS_TS_GENF_PPM_LOW_REG_L and
CPSW3_CPSW_NU_CPTS_TS_GENF_PPM_HIGH_REG_L) is:
(1,000,0000,000Hz/1pph)
* (3600 seconds/hour) = 34630B8A000 (hex)