14-11
Seiko Epson Corporation
S1C31D50 TECHNICAL MANUAL
(Rev. 1.00)
End pointer
Transfer source
SPIA_
n
RXD register address
Transfer destination
Memory address to which the last received data is stored
Control data
dst_inc
0x1 (+2)
dst_size
0x1 (haflword)
src_inc
0x3 (no increment)
src_size
0x1 (halfword)
R_power
0x0 (arbitrated for every transfer)
n_minus_1
Number of transfer data
cycle_ctrl
0x1 (basic transfer)
14.5.4.
Terminating Data Transfer in Master Mode
A procedure to terminate data transfer in master mode is shown below.
1.
Wait for an end-of-transmission interrupt (SPIA_
n
INTF.TENDIF bit = 1).
2.
Set the SPIA_
n
CTL.MODEN bit to 0 to disable the SPIA Ch.n operations.
3.
Stop the 16-bit timer to disable the clock supply to SPIA Ch.n.
14.5.5.
Data Transfer in Slave Mode
A data sending/receiving procedure and operations in slave mode are shown below. Figures
14.5.5.1 and 14.5.5.2 show a timing chart and flowcharts, respectively.
Data sending procedure
1.
Check to see if the SPIA_
n
INTF.TBEIF bit is set to 1 (transmit buffer empty).
2.
Write transmit data to the SPIA_
n
TXD register.
3.
Wait for a transmit buffer empty interrupt (SPIA_
n
INTF.TBEIF bit = 1).
4.
Repeat Steps 2 and 3 until the end of transmit data.
Note:
Transmit data must be written to the SPIA_
n
TXD register after the SPIA_
n
INTF.TBEIF bit is set to 1 by
the time the sending SPIA_
n
TXD register data written is completed. If no transmit data is written
during this period, the data bits input from the SDIn pin are shifted and output from the SDO
n
pin
without being modified.
Data receiving procedure
1.
Wait for a receive buffer full interrupt (SPIA_
n
INTF.RBFIF bit = 1).
2.
Read the received data from the SPIA_
n
RXD register.
3.
Repeat Steps 1 and 2 until the end of data reception.
Data transfer operations
The following shows the slave mode operations different from master mode:
•
Slave mode operates with the SPI clock supplied from the external SPI master to the SPICLK
n
pin.The data transfer rate is determined by the SPICLK
n
frequency. It is not necessary to
control the 16-bit timer.
•
SPIA can operate as a slave device only when the slave select signal input from the external SPI
master to the #SPISS
n
pin is set to the active (low) level. If #SPISS
n
= high, the software
transfer control, the SPICLK
n
pin input, and the SDI
n
pin input are all ineffective.
•
If the #SPISS
n
signal goes high during data transfer, the transfer bit counter is cleared and data
in the shift register is discarded.
•
Slave mode starts data transfer when SPICLK
n
is input from the external SPI master after the
#SPISS
n
signal is asserted. Writing transmit data is not a trigger to start data transfer.
Therefore, it is not necessary to write dummy data to the transmit data buffer when
performing data reception only.
•
Data transmission/reception can be performed even in SLEEP mode, it makes it possible to
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