Datasheet

 2017 Microchip Technology Inc. DS60001516A-page 757
SAM9G20
40.12.1.2 RMII Mode
Figure 40-7: EMAC RMII Timings
40.12.2 SPI
40.12.2.1 Maximum SPI Frequency
The following formulas give maximum SPI frequency in Master read and write modes and in Slave read and write modes.
• Master Write Mode
The SPI is only sending data to a slave device such as an LCD, for example. The limit is given by SPI
2
(or SPI
5
) timing. Since it
gives a maximum frequency above the maximum pad speed (see Section 40.6 “I/O Characteristics”), the maximum SPI frequency
is the one from the pad.
• Master Read Mode
t
valid
is the slave time response to output data after deleting an SPCK edge. For a non-volatile memory with t
valid
(or t
V
) = 12 ns
Max, f
SPCK
Max = 37.7 MHz @ V
DDIO
= 3.3V.
• Slave Read Mode
In slave mode, SPCK is the input clock for the SPI. The max SPCK frequency is given by setup and hold timings SPI
7
/SPI
8
(or SPI
10
/
SPI
11
). Since this gives a frequency well above the pad limit, the limit in slave read mode is given by SPCK pad.
Table 40-37: RMII Mode
Symbol Parameter Min (ns) Max (ns)
EMAC
21
ETXEN toggling from EREFCK rising 2 16
EMAC
22
ETX toggling from EREFCK rising 2 16
EMAC
23
Setup for ERX from EREFCK rising 4 –
EMAC
24
Hold for ERX from EREFCK rising 2 –
EMAC
25
Setup for ERXER from EREFCK rising 4 –
EMAC
26
Hold for ERXER from EREFCK rising 2 –
EMAC
27
Setup for ECRSDV from EREFCK rising 4 –
EMAC
28
Hold for ECRSDV from EREFCK rising 2 –
EREFCK
ETXEN
ETX[1:0]
ERX[1:0]
ERXER
ECRSDV
EMAC
21
EMAC
22
EMAC
23
EMAC
24
EMAC
25
EMAC
26
EMAC
27
EMAC
28
f
SPCK
Max
1
SPI
0
orSPI
3
()t
valid
+
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=