Datasheet
928
32142D–06/2013
ATUC64/128/256L3/4U
Note: 1. These values are based on simulation and characterization of other AVR microcontrollers manufactured in the same pro-
cess technology. These values are not covered by test limits in production.
Maximum SPI Frequency, Slave Input Mode
The maximum SPI slave input frequency is given by the following formula:
Where is the MOSI setup and hold time, SPI7 + SPI8 or SPI10 + SPI11 depending on
CPOL and NCPHA. is the maximum frequency of the CLK_SPI. Refer to the SPI chap-
ter for a description of this clock.
Maximum SPI Frequency, Slave Output Mode
The maximum SPI slave output frequency is given by the following formula:
Where is the MISO delay, SPI6 or SPI9 depending on CPOL and NCPHA. is the
SPI master setup time. Please refer to the SPI master datasheet for . is the max-
imum frequency of the SPI pins. Please refer to the I/O Pin Characteristics section for the
maximum frequency of the pins.
35.10.5 TWIM/TWIS Timing
Figure 35-45 shows the TWI-bus timing requirements and the compliance of the device with
them. Some of these requirements (t
r
and t
f
) are met by the device without requiring user inter-
vention. Compliance with the other requirements (t
HD-STA
, t
SU-STA
, t
SU-STO
, t
HD-DAT
, t
SU-DAT-TWI
, t
LOW-
TWI
, t
HIGH
, and f
TWCK
) requires user intervention through appropriate programming of the relevant
Table 35-44. SPI Timing, Slave Mode
(1)
Symbol Parameter Conditions Min Max Units
SPI6 SPCK falling to MISO delay
V
VDDIO
from
3.0V to 3.6V,
maximum
external
capacitor =
40pF
29.4
ns
SPI7 MOSI setup time before SPCK rises 0
SPI8 MOSI hold time after SPCK rises 6.0
SPI9 SPCK rising to MISO delay 29.0
SPI10 MOSI setup time before SPCK falls 0
SPI11 MOSI hold time after SPCK falls 5.5
SPI12 NPCS setup time before SPCK rises 3.4
SPI13 NPCS hold time after SPCK falls 1.1
SPI14 NPCS setup time before SPCK falls 3.3
SPI15 NPCS hold time after SPCK rises 0.7
f
SPCKMAX
MIN f
CLKSPI
1
SPIn
------------(,)=
SPIn
f
CLKSPI
f
SPCKMAX
MIN f
PINMAX
1
SPIn t
SETUP
+
------------------------------------(, )=
SPIn
t
SETUP
t
SETUP
f
PINMAX