
128
8008H–AVR–04/11
ATtiny48/88
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
Table 14-5). This means that the minimum SCK period will be two CPU
clock periods. When the SPI is configured as Slave, the SPI is only guaranteed to work at f
osc/4
or lower.
The SPI interface on the ATtiny48/88 is also used for program memory and EEPROM down-
loading or uploading. See
page 200 for serial programming and verification.
14.5.3
SPDR – SPI Data Register
The SPI Data Register is a read/write register used for data transfer between the Register File
and the SPI Shift Register. Writing to the register initiates data transmission. Reading the regis-
ter causes the Shift Register Receive buffer to be read.
Bit
765
43210
MSB
LSB
SPDR
Read/Write
R/W
Initial Value
XXXXXXX
X
Undefined