SPRUHX5I August 2014 – May 2024 TMS320F28374S , TMS320F28375S , TMS320F28375S-Q1 , TMS320F28376S , TMS320F28377S , TMS320F28377S-Q1 , TMS320F28378S , TMS320F28379S
Table 20-37 shows how you can select various sources to provide the receive frame-synchronization signal and the effect on the FSR pin. The polarity of the signal on the FSR pin is determined by the FSRP bit.
In digital loopback mode (DLB = 1), the transmit frame-synchronization signal is used as the receive frame-synchronization signal.
Also in the clock stop mode, the internal receive clock signal (MCLKR) and the internal receive frame-synchronization signal (FSR) are internally connected to their transmit counterparts, CLKX and FSX.
| Register | Bit | Name | Function | Type | Reset Value | |
|---|---|---|---|---|---|---|
| PCR | 10 | FSRM | Receive frame-synchronization mode | R/W | 0 | |
| FSRM = 0 | Receive frame synchronization is supplied by an external source via the FSR pin. | |||||
| FSRM = 1 | Receive frame synchronization is supplied by the sample rate generator. FSR is an output pin reflecting internal FSR, except when GSYNC = 1 in SRGR2. | |||||
| SRGR2 | 15 | GSYNC | Sample rate generator clock synchronization mode | R/W | 0 | |
| If the sample rate generator creates a frame-synchronization signal (FSG) that is derived from an external input clock, the GSYNC bit determines whether FSG is kept synchronized with pulses on the FSR pin. | ||||||
| GSYNC = 0 | No clock synchronization is used: CLKG oscillates without adjustment, and FSG pulses every (FPER + 1) CLKG cycles. | |||||
| GSYNC = 1 | Clock
synchronization is used. When a pulse is detected on the FSR pin:
|
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| SPCR1 | 15 | DLB | Digital loopback mode | R/W | 0 | |
| DLB = 0 | Digital loopback mode is disabled. | |||||
| DLB = 1 | Digital loopback mode is enabled. The receive signals, including the receive frame-synchronization signal, are connected internally through multiplexers to the corresponding transmit signals. | |||||
| SPCR1 | 12-11 | CLKSTP | Clock stop mode | R/W | 00 | |
| CLKSTP = 0Xb | Clock stop mode disabled; normal clocking for non-SPI mode. | |||||
| CLKSTP = 10b | Clock stop mode enabled without clock delay. The internal receive clock signal (MCLKR) and the internal receive frame-synchronization signal (FSR) are internally connected to their transmit counterparts, CLKX and FSX. | |||||
| CLKSTP = 11b | Clock stop mode enabled with clock delay. The internal receive clock signal (MCLKR) and the internal receive frame-synchronization signal (FSR) are internally connected to their transmit counterparts, CLKX and FSX. | |||||
| DLB | FSRM | GSYNC | Source of Receive Frame Synchronization |
FSR Pin Status |
|---|---|---|---|---|
| 0 | 0 | 0 or 1 | An external frame-synchronization signal enters the McBSP through the FSR pin. The signal is then inverted as determined by FSRP before being used as internal FSR. | Input |
| 0 | 1 | 0 | Internal FSR is driven by the sample rate generator frame-synchronization signal (FSG). | Output. FSG is inverted as determined by FSRP before being driven out on the FSR pin. |
| 0 | 1 | 1 | Internal FSR is driven by the sample rate generator frame-synchronization signal (FSG). | Input. The external frame-synchronization input on the FSR pin is used to synchronize CLKG and generate FSG pulses. |
| 1 | 0 | 0 | Internal FSX drives internal FSR. | High impedance |
| 1 | 0 or 1 | 1 | Internal FSX drives internal FSR. | Input. If the sample rate generator is running, external FSR is used to synchronize CLKG and generate FSG pulses. |
| 1 | 1 | 0 | Internal FSX drives internal FSR. | Output. Receive (same as transmit) frame synchronization is inverted as determined by FSRP before being driven out on the FSR pin. |