atmega32c1 ATMEL Corporation, atmega32c1 Datasheet - Page 164

• Manufacturer Part Number: atmega32c1
• Description: Atmega32m1 Automotive 8-bit Avr Microcontroller With 32k/64k Bytes In-system Programmable Flash
• Manufacturer: ATMEL Corporation

15.2.5
164
ATmega32/64/M1/C1
SPI Status Register – SPSR
These two bits control the SCK rate of the device configured as a Master. SPR1 and SPR0 have
no effect on the Slave. The relationship between SCK and the clk
the following table:
Table 15-4.
• Bit 7 – SPIF: SPI Interrupt Flag
When a serial transfer is complete, the SPIF flag is set. An interrupt is generated if SPIE in
SPCR is set and global interrupts are enabled. If SS is an input and is driven low when the SPI is
in Master mode, this will also set the SPIF flag. SPIF is cleared by hardware when executing the
corresponding interrupt handling vector. Alternatively, the SPIF bit is cleared by first reading the
SPI Status Register with SPIF set, then accessing the SPI Data Register (SPDR).
• Bit 6 – WCOL: Write COLlision Flag
The WCOL bit is set if the SPI Data Register (SPDR) is written during a data transfer. The
WCOL bit (and the SPIF bit) are cleared by first reading the SPI Status Register with WCOL set,
and then accessing the SPI Data Register.
• Bit 5..1 – Res: Reserved Bits
These bits are reserved bits in the ATmega32/64/M1/C1 and will always read as zero.
• Bit 0 – SPI2X: Double SPI Speed Bit
When this bit is written logic one the SPI speed (SCK Frequency) will be doubled when the SPI
is in Master mode (see
clock periods. When the SPI is configured as Slave, the SPI is only guaranteed to work at f
or lower.
The SPI interface on the ATmega32/64/M1/C1 is also used for program memory and EEPROM
downloading or uploading. See
verification.
Bit
Read/Write
Initial Value
SPI2X
0
0
0
0
1
1
1
1
Relationship Between SCK and the Oscillator Frequency
SPIF
R
7
0
Table
WCOL
SPR1
6
R
0
0
0
1
1
0
0
1
1
15-4). This means that the minimum SCK period will be two CPU
Serial Programming Algorithm305
R
5
–
0
SPR0
4
–
R
0
0
1
0
1
0
1
0
1
R
3
–
0
SCK Frequency
f
f
f
f
f
f
f
f
clkio
clkio
clkio
clkio
clkio
clkio
clkio
clkio
/
/
/
/
/
/
/
/
4
16
64
128
2
8
32
64
2
–
R
0
IO
for serial programming and
frequency f
R
1
–
0
SPI2X
R/W
0
0
clkio
7647A–AVR–02/08
is shown in
SPSR
clkio
/4