ST92P141K4D0 View Datasheet(PDF) - STMicroelectronics
Part Name
Description
Manufacturer
ST92P141K4D0 Datasheet PDF : 179 Pages
| |||
ST92141 - SERIAL PERIPHERAL INTERFACE (SPI)
SERIAL PERIPHERAL INTERFACE (Cont’d)
7.5.6 Register Description
DATA REGISTER (SPDR)
R240 - Read/Write
Register Page: 7
Reset Value: 0000 0000 (00h)
7
0
D7 D6 D5 D4 D3 D2 D1 D0
The DR register is used to transmit and receive
data on the serial bus. In the master device only a
write to this register will initiate transmission/re-
ception of another byte.
Notes: During the last clock cycle the SPIF bit is
set, a copy of the received data byte in the shift
register is moved to a buffer. When the user reads
the serial peripheral data register, the buffer is ac-
tually being read.
Warning: A write to the DR register places data di-
rectly into the shift register for transmission.
A read to the DR register returns the value located
in the buffer and not the content of the shift regis-
ter (see Figure 73).
CONTROL REGISTER (SPCR)
R241 - Read/Write
Register Page: 7
Reset Value: 0000 0000 (00h)
7
0
SPIE SPOE SPIS MSTR CPOL CPHA SPR1 SPR0
Bit 7 = SPIE Serial peripheral interrupt enable.
This bit is set and cleared by software.
0: Interrupt is inhibited
1: An SPI interrupt is generated whenever either
SPIF or MODF are set in the SR register while
the other flag is 0.
Bit 6 = SPOE Serial peripheral output enable.
This bit is set and cleared by software. It is also
cleared by hardware when, in master mode, SS=0
(see Section 7.5.4.5 Master Mode Fault).
0: SPI alternate functions disabled (MISO, MOSI
and SCK can only work as input)
1: SPI alternate functions enabled (MISO, MOSI
and SCK can work as input or output depending
on the value of MSTR)
Note: To use the MISO, MOSI and SCK alternate
functions (input or output), the corresponding I/O
port must be programmed as alternate function
output.
Bit 5 = SPIS Interrupt Selection.
This bit is set and cleared by software.
0: Interrupt source is external interrupt
1: Interrupt source is SPI
Bit 4 = MSTR Master.
This bit is set and cleared by software. It is also
cleared by hardware when, in master mode, SS=0
(see Section 7.5.4.5 Master Mode Fault).
0: Slave mode is selected
1: Master mode is selected, the function of the
SCK pin changes from an input to an output and
the functions of the MISO and MOSI pins are re-
versed.
Bit 3 = CPOL Clock polarity.
This bit is set and cleared by software. This bit de-
termines the steady state of the serial Clock. The
CPOL bit affects both the master and slave
modes.
0: The steady state is a low value at the SCK pin.
1: The steady state is a high value at the SCK pin.
Bit 2 = CPHA Clock phase.
This bit is set and cleared by software.
0: The first clock transition is the first data capture
edge.
1: The second clock transition is the first capture
edge.
Bit 1:0 = SPR[1:0] Serial peripheral rate.
These bits are set and cleared by software. They
select one of four baud rates to be used as the se-
rial clock when the device is a master.
These 2 bits have no effect in slave mode.
Table 28. Serial Peripheral Baud Rate
INTCLK Clock Divide
2
4
16
32
SPR1
0
0
1
1
SPR0
0
1
0
1
145/179
9
Share Link: 