em78f644nso28s ELAN Microelectronics Corp, em78f644nso28s Datasheet - Page 113

• Manufacturer Part Number: em78f644nso28s
• Description: Flash Series 8-bit Microcontroller
• Manufacturer: ELAN Microelectronics Corp

Product Specification (V1.0) 05.05.2010
(This specification is subject to change without further notice)
The following will describe the functions of each block and on how to carry out the
SPI communication with the signals depicted in Figures 6-16a and 6-16b above.
6.7.3 SPI Signal & Pin Description
The detailed functions of the four pins, SI, SO, SCK, and /SS are as follows:
SI: Serial Data In
SO: Serial Data Out
SCK: Serial Clock
/SS: /Slave Select (Option). This pin (/SS) may be required during a Slave
mode
RBF: Set by Buffer Full Detector
Buffer Full Detector: Set to “1” when an 8-bit shifting is completed.
SSE: Loads the data in SPIS register, and begin to shift. The SSE bit is kept at
“1” while communication is continuing and to determine if the next write attempt
is available. This flag must be cleared when shifting is completed.
SPIS reg.: Shifting byte in and out. The MSB is shifted first. Both the SPIR and
the SPIW registers are shifted at the same time. Once data are written, SPIS
starts transmission / reception. The data received will be moved to the SPIR
register as the shifting of the 8-bit data is completed. The RBF (Read Buffer Full)
flag and the SPIIF (SPI Interrupt) flag are then set.
SPIR reg.: Read buffer. The buffer will be updated as the 8-bit shifting is
completed. The data must be read before the next reception is completed. The
RBF flag is cleared as the SPIR register is being read.
SPIW reg.: Write buffer. The buffer will deny any attempts to write until the 8-bit
shifting is completed.
SBRS2~SBRS0: Programming the clock frequency/rates and sources.
Clock Select: Selecting either the internal or the external clock as the shifting
clock.
Edge Select: Selecting the appropriate clock edges by programming the CES
bit
SI:
●
●
●
Serial Data In
Receive in sequential order. The Most Significant Bit (MSB) first, the Least
Significant Bit (LSB) last.
Defined as high-impedance, if not selected.
EM78F648/644/642/641/548/544/542/541N
8-Bit Microcontroller
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