AT89C5122 ATMEL [ATMEL Corporation], AT89C5122 Datasheet - Page 139

• Manufacturer Part Number: AT89C5122
• Description: MICROCONTROLLER WITH USB AND SMART CARD READER INTERFACES
• Manufacturer: ATMEL [ATMEL Corporation]

Functional Description
Operating Modes
4202D–SCR–06/05
Figure 84 shows a detailed structure of the SPI module.
Figure 84. SPI Module Block Diagram
The Serial Peripheral Interface can be configured as one of the two modes: Master
mode or Salve mode. The configuration and initialization of the SPI module is made
through one register:
•
Once the SPI is configured, the data exchange is made using:
•
•
•
During an SPI transmission, data is simultaneously transmitted (shifted out serially) and
received (shifted in serially). A serial clock line (SCK) synchronizes shifting and sam-
pling on the two serial data lines (MOSI and MISO). A Slave Select line (SS) allows
individual selection of a Slave SPI device; Slave devices that are not selected do not
interfere with SPI bus activities.
When the Master device transmits data to the Slave device via the MOSI line, the Slave
device responds by sending data to the Master device via the MISO line. This implies
full-duplex transmission with both data out and data in synchronized with the same clock
(Figure 85).
SPI Interrupt Request
The Serial Peripheral Control register (SPCON)
SPCON
The Serial Peripheral Status register (SPSTA)
The Serial Peripheral Data register (SPDAT)
Clock
Divider
IntClk
SPR2
/128
/32
/64
/16
SPEN
/8
/4
Clock
Select
SSDIS
MSTR
Receive Data Register
SPIF
CPOL
7
Shift Register
WCOL
Internal Bus
6
CPHA
5
SPI
Control
4
3
SPR1
-
2
Clock
Logic
SPCON
1
SPDAT
MODF
SPR0
0
-
M
S
Pin
Control
Logic
-
-
SPSTA
-
8-bit bus
1-bit signal
MOSI
MISO
SS
SCK
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