AT91SAM7SE256B-AU Atmel, AT91SAM7SE256B-AU Datasheet - Page 328
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AT91SAM7SE256B-AU
Manufacturer Part Number
AT91SAM7SE256B-AU
Description
IC ARM7 MCU FLASH 256K 128-LQFP
Manufacturer
Atmel
Series
AT91SAMr
Datasheet
1.AT91SAM7SE256-AU.pdf
(673 pages)
Specifications of AT91SAM7SE256B-AU
Core Processor
ARM7
Core Size
16/32-Bit
Speed
55MHz
Connectivity
EBI/EMI, I²C, SPI, SSC, UART/USART, USB
Peripherals
Brown-out Detect/Reset, POR, PWM, WDT
Number Of I /o
88
Program Memory Size
256KB (256K x 8)
Program Memory Type
FLASH
Ram Size
32K x 8
Voltage - Supply (vcc/vdd)
1.65 V ~ 1.95 V
Data Converters
A/D 8x10b
Oscillator Type
Internal
Operating Temperature
-40°C ~ 85°C
Package / Case
*
Core
ARM7TDMI
Lead Free Status / RoHS Status
Lead free / RoHS Compliant
Eeprom Size
-
Lead Free Status / Rohs Status
Details
Available stocks
Company
Part Number
Manufacturer
Quantity
Price
- Current page: 328 of 673
- Download datasheet (11Mb)
31.6.3
Master Mode Operations
When configured in Master Mode, the SPI operates on the clock generated by the internal pro-
grammable baud rate generator. It fully controls the data transfers to and from the slave(s)
connected to the SPI bus. The SPI drives the chip select line to the slave and the serial clock
signal (SPCK).
The SPI features two holding registers, the Transmit Data Register and the Receive Data Regis-
ter, and a single Shift Register. The holding registers maintain the data flow at a constant rate.
After enabling the SPI, a data transfer begins when the processor writes to the SPI_TDR (Trans-
mit Data Register). The written data is immediately transferred in the Shift Register and transfer
on the SPI bus starts. While the data in the Shift Register is shifted on the MOSI line, the MISO
line is sampled and shifted in the Shift Register. Transmission cannot occur without reception.
Before writing the TDR, the PCS field must be set in order to select a slave.
If new data is written in SPI_TDR during the transfer, it stays in it until the current transfer is
completed. Then, the received data is transferred from the Shift Register to SPI_RDR, the data
in SPI_TDR is loaded in the Shift Register and a new transfer starts.
The transfer of a data written in SPI_TDR in the Shift Register is indicated by the TDRE bit
(Transmit Data Register Empty) in the Status Register (SPI_SR). When new data is written in
SPI_TDR, this bit is cleared. The TDRE bit is used to trigger the Transmit PDC channel.
The end of transfer is indicated by the TXEMPTY flag in the SPI_SR register. If a transfer delay
(DLYBCT) is greater than 0 for the last transfer, TXEMPTY is set after the completion of said
delay. The master clock (MCK) can be switched off at this time.
The transfer of received data from the Shift Register in SPI_RDR is indicated by the RDRF bit
(Receive Data Register Full) in the Status Register (SPI_SR). When the received data is read,
the RDRF bit is cleared.
If the SPI_RDR (Receive Data Register) has not been read before new data is received, the
Overrun Error bit (OVRES) in SPI_SR is set. As long as this flag is set, data is loaded in
SPI_RDR. The user has to read the status register to clear the OVRES bit.
Figure 31-5 on page 329
shows a block diagram of the SPI when operating in Master Mode.
Fig-
ure 31-6 on page 330
shows a flow chart describing how transfers are handled.
SAM7SE512/256/32 Preliminary
328
6222F–ATARM–14-Jan-11
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