at91sam9263 ATMEL Corporation, at91sam9263 Datasheet - Page 203

• Manufacturer Part Number: at91sam9263
• Description: At91 Arm Thumb Microcontrollers
• Manufacturer: ATMEL Corporation

21.8.1.2
21.8.1.3
21.8.1.4
6249D–ATARM–20-Dec-07
NCS Waveform
Read Cycle
Null Delay Setup and Hold
Similarly, the NCS signal can be divided into a setup time, pulse length and hold time:
The NRD_CYCLE time is defined as the total duration of the read cycle, i.e., from the time where
address is set on the address bus to the point where address may change. The total read cycle
time is equal to:
NRD_CYCLE = NRD_SETUP + NRD_PULSE + NRD_HOLD
= NCS_RD_SETUP + NCS_RD_PULSE + NCS_RD_HOLD
All NRD and NCS timings are defined separately for each chip select as an integer number of
Master Clock cycles. To ensure that the NRD and NCS timings are coherent, user must define
the total read cycle instead of the hold timing. NRD_CYCLE implicitly defines the NRD hold time
and NCS hold time as:
NRD_HOLD = NRD_CYCLE - NRD SETUP - NRD PULSE
NCS_RD_HOLD = NRD_CYCLE - NCS_RD_SETUP - NCS_RD_PULSE
If null setup and hold parameters are programmed for NRD and/or NCS, NRD and NCS remain
active continuously in case of consecutive read cycles in the same memory (see
1. NCS_RD_SETUP: the NCS setup time is defined as the setup time of address before
2. NCS_RD_PULSE: the NCS pulse length is the time between NCS falling edge and
3. NCS_RD_HOLD: the NCS hold time is defined as the hold time of address after the
the NCS falling edge.
NCS rising edge;
NCS rising edge.
AT91SAM9263 Preliminary
Figure
21-9).
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