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External Control
For different audio processing control requirements, in addition to the internal MCU
connections, external SPI control is also supported. However, before using the external
control, some relevant initialisation must be executed which includes the PLL, Reset and
SPI path. After the PLL is setup and the audio processor is reset (the flow is the same as
with the previous unit), set SPICR[7](IEMC)=0 to switch the SPI path to be the external
pin-shared port so that the external SPI command can be executed. The five occupied
I/O ports cannot be used for other functions at this time.
SPICK
SPICR[7]=
SPICR[3]
1
SPICR[7]=
PC6
0
Points to note when using external control:
When required to reduce the PLL frequency or entering the sleep mode
When the SPI is returned to the internal MCU control
Usable pins decrease
For the above problems 1 and 2, it is recommended to use an external SPI controller and
the internal MCU with master/slave signals or establish a control protocol, for the
objective of internal register control for frequency adjustment or audio processor control.
This will reduce the loading on the master MCU (external MCU) for calculations and flow
control. See the following for description:
External MCU Connection Diagram
HT98R068 Two-way Radio MCU
MOSI
MISO
SPICR[2]
SPICR[1]
PC4
PA5
SPI Control Signal Table
11
SPISS
SPIRQ
SPICR[4]
SPICR[0]
PC7
PC5
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