AT91SAM7SE256B-AUR Atmel, AT91SAM7SE256B-AUR Datasheet - Page 170

• Manufacturer Part Number: AT91SAM7SE256B-AUR
• Description: IC ARM7 MCU FLASH 256K 128-LQFP
• Manufacturer: Atmel
• Series: AT91SAMr

Specifications of AT91SAM7SE256B-AUR

• Core Processor: ARM7
• Core Size: 16/32-Bit
• Speed: 55MHz
• Connectivity: EBI/EMI, I²C, SPI, SSC, UART/USART, USB
• Peripherals: Brown-out Detect/Reset, POR, PWM, WDT
• Number Of I /o: 88
• Program Memory Size: 256KB (256K x 8)
• Program Memory Type: FLASH
• Ram Size: 32K x 8
• Voltage - Supply (vcc/vdd): 1.65 V ~ 1.95 V
• Data Converters: A/D 8x10b
• Oscillator Type: Internal
• Operating Temperature: -40°C ~ 85°C
• Package / Case: *
• Processor Series: SAM7SE256
• Core: ARM7TDMI
• Data Bus Width: 32 bit
• Data Ram Size: 32 KB
• Interface Type: SPI, USB
• Maximum Clock Frequency: 48 MHz
• Number Of Programmable I/os: 88
• Maximum Operating Temperature: + 85 C
• Mounting Style: SMD/SMT
• Operating Temperature Range: - 40 C to + 85 C
• Processor To Be Evaluated: AT91SAM7SE256B
• Supply Current (max): 60 uA
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Eeprom Size: -
• Lead Free Status / Rohs Status: Details

22.6.4.1
22.6.4.2
170
SAM7SE512/256/32 Preliminary
Standard Wait States
External Wait States
Each chip select can be programmed to insert one or more wait states during an access on the
corresponding memory area. This is done by setting the WSEN field in the corresponding
SMC_CSR
grammed in the NWS field in the same register.
Below is the correspondence between the number of standard wait states programmed and the
number of clock cycles during which the NWE pulse is held low:
For each additional wait state programmed, an additional cycle is added.
Figure 22-13. One Standard Wait State Access
Notes:
The NWAIT input pin is used to insert wait states beyond the maximum standard wait states pro-
grammable or in addition to. If NWAIT is asserted low, then the SMC adds a wait state and no
changes are made to the output signals, the internal counters or the state. When NWAIT is de-
asserted, the SMC completes the access sequence.
WARNING: Asserting NWAIT low stops the core’s clock and thus stops program execution.
The input of the NWAIT signal is an asynchronous input. To avoid any metastability problems,
NWAIT is synchronized before using it. This operation results in a two-cycle delay.
NWS must be programmed as a function of synchronization time and delay between NWAIT fall-
ing and control signals falling (NRD/NWE), otherwise SMC will not function correctly.
Note:
WARNING: If NWAIT is asserted during a setup or hold timing, the SMC does not function
correctly.
0 wait states
1 wait state
NWS
1. Early Read Protocol
2. Standard Read Protocol
Where external NWAIT synchronization is equal to 2 cycles.
The minimum value for NWS if NWAIT is used, is 3.
(“SMC Chip Select Registers” on page
≥
Wait Delay from nrd/nwe
A[22:0]
NWE
MCK
NRD
NCS
(1)
1 Wait State Access
(2)
+
external_nwait Synchronization Delay
1/2 clock cycle
1 clock cycle
196). The number of cycles to insert is pro-
6222F–ATARM–14-Jan-11
+
1