CYRF69103
Document #: 001-07611 Rev *C
Page 11 of 65
SPI Communication and Transactions
The SPI transactions can be single byte or multi-byte. The MCU
function initiates a data transfer through a Command/Address
byte. The following bytes are data bytes. The SPI transaction
format is shown in Figure 4.
The DIR bit specifies the direction of data transfer. 0 = Master
reads from slave. 1 = Master writes to slave.
The INC bit helps to read or write consecutive bytes from
contiguous memory locations in a single burst mode operation.
If Slave Select is asserted and INC = 1, then the master MCU
function reads a byte from the radio, the address is incremented
by a byte location, and then the byte at that location is read, and
so on.
If Slave Select is asserted and INC = 0, then the MCU function
reads/writes the bytes in the same register in burst mode, but if
it is a register file then it reads/writes the bytes in that register file.
The SPI interface between the radio function and the MCU is not
dependent on the internal 12-MHz oscillator of the radio.
Therefore, radio function registers can be read from or written
into while the radio is in sleep mode.
SPI IO Voltage References
The SPI interfaces between MCU function and the radio and the
IRQ and RST have a separate voltage reference VIO. For
CYRF69103 VIO is normally set to VCC.
SPI Connects to External Devices
The three SPI wires, MOSI, SCK, and SS are also drawn out of
the package as external pins to allow the user to interface their
own external devices (such as optical sensors and others)
through SPI. The radio function also has its own SPI wires MISO
and IRQ, which can be used to send data back to the MCU
function or send an interrupt request to the MCU function. They
can also be configured as GPIO pins.
CPU Architecture
This family of microcontrollers is based on a high-performance,
8-bit, Harvard architecture microprocessor. Five registers control
the primary operation of the CPU core. These registers are
affected by various instructions, but are not directly accessible
through the register space by the user.
The 16-bit Program Counter Register (CPU_PC) allows for direct
addressing of the full eight Kbytes of program memory space.
The Accumulator Register (CPU_A) is the general-purpose
register that holds the results of instructions that specify any of
the source addressing modes.
The Index Register (CPU_X) holds an offset value that is used
in the indexed addressing modes. Typically, this is used to
address a block of data within the data memory space.
The Stack Pointer Register (CPU_SP) holds the address of the
current top-of-stack in the data memory space. It is affected by
the PUSH, POP, LCALL, CALL, RETI, and RET instructions,
which manage the software stack. It can also be affected by the
SWAP and ADD instructions.
The Flag Register (CPU_F) has three status bits: Zero Flag bit
[1]; Carry Flag bit [2]; Supervisory State bit [3]. The Global
Interrupt Enable bit [0] is used to globally enable or disable inter-
rupts. The user cannot manipulate the Supervisory State status
bit [3]. The flags are affected by arithmetic, logic, and shift opera-
tions. The manner in which each flag is changed is dependent
upon the instruction being executed (for example, AND, OR,
XOR). See Table 22.
Table 4. SPI Transaction Format
Byte 1
Byte 1+N
Bit #
7
6
[5:0]
[7:0]
Bit Name
DIR
INC
Address
Data
Table 5. CPU Registers and Register Name
Register
Register Name
Flags
CPU_F
Program Counter
CPU_PC
Accumulator
CPU_A
Stack Pointer
CPU_SP
Index
CPU_X
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