Symphony DSP56724/DSP56725 Multi-Core Audio Processors, Rev. 0
10-8
Freescale Semiconductor
Serial Host Interface (SHI, SHI_1)
Figure 10-6. SPI Data-To-Clock Timing Diagram
If the CPOL bit is cleared, it produces a steady-state low value at the SCK pin of the master device
whenever data is not being transferred. If the CPOL bit is set, it produces a high value at the SCK pin of
the master device whenever data is not being transferred.
The CPHA and CPOL bits together select the desired clock-to-data relationship. In general, the CPHA bit
selects the clock edge that captures data and allows it to change states. It has its greatest impact on the first
bit transmitted (MSB) in that it does or does not allow a clock transition before the data capture edge.
•
When the SHI is in slave mode and CPHA bit = 0, the SS line must be deasserted and asserted by
the external master between each successive word transfer. Also, the SS line must remain asserted
between successive bytes within a word. The DSP core should write the next data word to the HTX
register when the HTDE bit = 1, thereby clearing the HTDE bit. However, the data is transferred
to the shift register for transmission only when the SS line is deasserted. The HTDE bit is set when
the data is transferred from the HTX register to the shift register.
•
When the SHI is in slave mode and CPHA bit = 1, the SS line may remain asserted between
successive word transfers. Also, the SS line must remain asserted between successive bytes within
a word. The DSP core should write the next data word to HTX register when HTDE bit = 1,
thereby clearing the HTDE bit. The HTX register data is transferred to the shift register for
transmission as soon as the shift register is empty. The HTDE bit is set when the data is transferred
from the HTX register to the shift register.
•
When the SHI is in master mode and CPHA bit = 0, the DSP core should write the next data word
to the HTX register when HTDE bit = 1, thereby clearing the HTDE bit. The data is transferred
immediately to the shift register for transmission. The HTDE bit is set only at the end of the data
word transmission.
•
The master is responsible for deasserting and asserting the slave device SS line between word
transmissions.
MSB
6
5
4
3
2
1
LSB
MISO/MOSI
Internal Strobe for Data Capture
SCK (CPOL = 1, CPHA = 1
SCK (CPOL = 1, CPHA = 0
SCK (CPOL = 0, CPHA = 1
SCK (CPOL = 0, CPHA = 0
SS
Содержание Symphony DSP56724
Страница 22: ...Symphony DSP56724 DSP56725 Multi Core Audio Processors Rev 0 1 10 Freescale Semiconductor Introduction ...
Страница 52: ...Symphony DSP56724 DSP56725 Multi Core Audio Processors Rev 0 2 30 Freescale Semiconductor Signal Descriptions ...
Страница 112: ...Symphony DSP56724 DSP56725 Multi Core Audio Processors Rev 0 7 12 Freescale Semiconductor Clock Generation Module CGM ...
Страница 244: ...Symphony DSP56724 DSP56725 Multi Core Audio Processors Rev 0 14 6 Freescale Semiconductor Shared Bus Arbiter ...
Страница 246: ...Symphony DSP56724 DSP56725 Multi Core Audio Processors Rev 0 15 2 Freescale Semiconductor Shared Memory Shared Memory ...