Texas Instruments CC2650DK ユーザーズマニュアル
Samplestamp Generator
22.8.2 Starting Input and Output Pins
The [I2S:STMPINTRIG] and [I2S:STMPOUTTRIG] registers contain WCLK counter compare values that
are used to start the input and output audio streaming, respectively:
are used to start the input and output audio streaming, respectively:
•
When the WCLK counter value reaches the [I2S:STMPINTRIG] register and the
[I2S:STMPCTL:IN_RDY] register is set, the memory interface controller begins storing samples to
memory in the next frame: ((STMPINTRIG + 1) % STMPWPER).
[I2S:STMPCTL:IN_RDY] register is set, the memory interface controller begins storing samples to
memory in the next frame: ((STMPINTRIG + 1) % STMPWPER).
•
When the WCLK counter value reaches the [I2S:STMPOUTTRIG] register and the
[I2S:STMPCTL.OUT_RDY] register is set, the memory interface controller begins outputting samples
loaded from memory in the next frame: ((STMPINTRIG + 1) % STMPWPER).
[I2S:STMPCTL.OUT_RDY] register is set, the memory interface controller begins outputting samples
loaded from memory in the next frame: ((STMPINTRIG + 1) % STMPWPER).
22.8.3 Samplestamp Capturing
A pulse on samplestamp_req captures the XOSC and WCLK counter values for later retrieval:
•
[I2S:STMPXCNTCAPTn] = the XOSC counter at time of capture
•
[I2S:STMPXPER] = the number of XOSC cycles in the previous WCLK period
•
[I2S:STMPWCNTCAPTn] = the WCLK counter at time of capture
The samplestamp value used is a fixed-point number, INT.FRAC, where:
•
INT = [I2S:STMPWCNTCAPTn]
•
FRAC = [I2S:STMPXCNTCAPTn] and [I2S:STMPXPER]
NOTE:
Because the [I2S:STMPXPER] register is in the previous period value, saturation of
[I2S:STMPXCNTCAPTn] must be handled in software (if required).
NOTE:
The samplestamp_req pulse can be generated by different radio events that are configured
outside the I2S module, see the [EVENT:I2SSTMPSEL0] register.
1420
Integrated Interchip Sound (I2S) Module
SWCU117A – February 2015 – Revised March 2015
Copyright © 2015, Texas Instruments Incorporated