Datasheet

 2017 Microchip Technology Inc. DS60001516A-page 159
SAM9G20
20.8.3 Write Waveforms
The write protocol is similar to the read protocol. It is depicted in Figure 20-12. The write cycle starts with the address setting on the mem-
ory address bus.
20.8.3.1 NWE Waveforms
The NWE signal is characterized by a setup timing, a pulse width and a hold timing.
1. NWE_SETUP: the NWE setup time is defined as the setup of address and data before the NWE falling edge;
2. NWE_PULSE: The NWE pulse length is the time between NWE falling edge and NWE rising edge;
3. NWE_HOLD: The NWE hold time is defined as the hold time of address and data after the NWE rising edge.
The NWE waveforms apply to all byte-write lines in Byte Write access mode: NWR0 to NWR3.
20.8.3.2 NCS Waveforms
The NCS signal waveforms in write operation are not the same that those applied in read operations, but are separately defined:
1. NCS_WR_SETUP: the NCS setup time is defined as the setup time of address before the NCS falling edge.
2. NCS_WR_PULSE: the NCS pulse length is the time between NCS falling edge and NCS rising edge;
3. NCS_WR_HOLD: the NCS hold time is defined as the hold time of address after the NCS rising edge.
Figure 20-12: Write Cycle
20.8.3.3 Write Cycle
The write-cycle time is defined as the total duration of the write cycle, that is, from the time where address is set on the address bus to the
point where address may change. The total write cycle time is equal to:
NWE_CYCLE = NWE_SETUP + NWE_PULSE + NWE_HOLD
= NCS_WR_SETUP + NCS_WR_PULSE + NCS_WR_HOLD
All NWE and NCS (write) timings are defined separately for each chip select as an integer number of Master Clock cycles. To ensure that
the NWE and NCS timings are coherent, the user must define the total write cycle instead of the hold timing. This implicitly defines the
NWE hold time and NCS (write) hold times as:
NWE_HOLD = NWE_CYCLE - NWE_SETUP - NWE_PULSE
NCS_WR_HOLD = NWE_CYCLE - NCS_WR_SETUP - NCS_WR_PULSE
A
[25:2]
NBS0, NBS1,
NBS2, NBS3,
A0, A1
NCS
NWE_SETUP NWE_PULSE NWE_HOLD
MCK
NWE
NCS_WR_SETUP
NCS_WR_PULSE
NCS_WR_HOLD
NWE_CYCLE