AT8xC51SND2C
Configuration
The SPI configuration is made through SPCON.
Master Configuration
Slave Configuration
The SPI operates in master mode when the MSTR bit in SPCON is set.
The SPI operates in slave mode when the MSTR bit in SPCON is cleared and data has
been loaded is SPDAT.
Data Exchange
There are 2 possible methods to exchange data in master and slave modes:
•
•
polling
interrupts
Master Mode with Polling
Policy
Figure 110 shows the initialization phase and the transfer phase flows using the polling
method. Using this flow prevents any overrun error occurrence.
The bit rate is selected according to Table 154. The transfer format depends on the
slave peripheral.
SS may be deasserted between transfers depending also on the slave peripheral.
SPIF flag is cleared when reading SPDAT (SPSTA has been read before by the “end of
transfer” check).
This polling method provides the fastest effective transmission and is well adapted when
communicating at high speed with other microcontrollers. However, the procedure may
then be interrupted at any time by higher priority tasks.
Figure 110. Master SPI Polling Flows
SPI Initialization
Polling Policy
SPI Transfer
Polling Policy
Disable interrupt
Select Slave
SPIE = 0
Pn.x = L
Select Master Mode
Start Transfer
MSTR = 1
write data in SPDAT
Select Bit Rate
program SPR2:0
End Of Transfer?
SPIF = 1?
Select Format
program CPOL & CPHA
Get Data Received
read SPDAT
Enable SPI
SPEN = 1
Last Transfer?
Deselect Slave
Pn.x = H
163
4341D–MP3–04/05
ATMEL [ ATMEL ]
