MCIMX281AVM4B Freescale Semiconductor, MCIMX281AVM4B Datasheet - Page 1099

• Manufacturer Part Number: MCIMX281AVM4B
• Description: IC MPU I.MX28 1.2 289MAPBGA
• Manufacturer: Freescale Semiconductor
• Series: i.MX28r

Specifications of MCIMX281AVM4B

• Core Processor: ARM9
• Core Size: 32-Bit
• Speed: 454MHz
• Connectivity: CAN, EBI/EMI, Ethernet, I²C, MMC, SmartCard, SPI, SSI, UART/USART, USB OTG
• Peripherals: DMA, I²S, LCD, POR, PWM, WDT
• Program Memory Size: 128KB (32K x 32)
• Program Memory Type: Mask ROM
• Ram Size: 32K x 32
• Voltage - Supply (vcc/vdd): 1.25 V ~ 5.25 V
• Data Converters: A/D 17x12b
• Oscillator Type: External
• Operating Temperature: -40°C ~ 85°C
• Package / Case: 289-LFBGA
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Number Of I /o: -
• Eeprom Size: -
• Lead Free Status / Rohs Status: Supplier Unconfirmed

Chapter 14 External Memory Interface (EMI)
14.7.5 Read Data Capture
When reading, DDR (dual data rate) devices send a data strobe (DQS) signal coincident
with the read data. The edges of this DQS strobe are aligned (edge-aligned) with the data
output by the DDR devices.
To latch read data into the EMI read data buffer, it is required that the latch clock edge is
center-aligned with the data. Thus, a delayed version of the DQS strobe signal must be used
to capture the data. Because the frequency of the DQS strobe signal is matched to the
emi_clk, the delay is a relative number based on the period of the emi_clk. In the example
shown below, the delay is set to approximately 25% of the emi_clk cycle.
emi_clk
io_dqs_in
d0
d1
d2
d3
io_dq_in
dqs delay = 1/4 cycle
delayed_dqs
capture data by the rise & fall edge of delayed _dqs
Figure 14-10. Read Data Capture
14.7.6 Synchronize Read Data From delayed_dqs to emi_clk
Domain
Read data is captured into data buffers by the delayed_dqs. It need to be synchronized to
the emi_clk domain, then returned to EMI core logic.
The following figure illustrates how the read data from an external DRAM device was
captured and synchronized to EMI core logic.
i.MX28 Applications Processor Reference Manual, Rev. 1, 2010
Freescale Semiconductor, Inc.
1099