Serial Host Interface (SHI, SHI_1)
Symphony DSP56724/DSP56725 Multi-Core Audio Processors, Rev. 0
Freescale Semiconductor
10-3
10.3
SHI Clock Generator
If the interface operates in master mode, the SHI clock generator generates the SHI serial clock. If the
interface operates in slave mode, the SHI clock generator is disabled, except if the interface is in I
2
C mode
when the HCKFR bit is set in the HCKR register.
When the SHI operates in slave mode, the clock is external and is input to the SHI (HMST = 0).
shows the internal clock path connections. It is the user’s responsibility to select the proper
clock rate within the correct range (defined in the I
2
C and SPI bus specifications).
Figure 10-2. SHI Clock Generator
10.3.1
Serial Host Interface Programming Model
The Serial Host Interface programming model has two parts: a Host side and a DSP side.
•
Host side—See
Section 10.3.2, “SHI Input/Output Shift Register (IOSR)—Host
Side.”
•
DSP side—See
Section 10.3.3, “SHI Host Transmit Data Register (HTX)—DSP
”
through
Section 10.3.8, “SHI Control/Status Register (HCSR)—DSP Side.”
Figure 10-3. SHI Programming Model—Host Side
HDM0 - HDM7
HRS
CPHA, CPOL, HI
2
C
HMST
SHI Clock
SHI
Controller
Clock Logic
Divide by
1 or 8
Divide by 1
to
Divide by 256
Divide
by 2
SCK/SCL
F
SYS
HMST = 1
HMST = 0
0
I/O Shift Register (IOSR)
IOSR
23
AA0418