MultiMediaCard (MMC)

Three other signals shown on the connector are COMM and the mechanical switches write protect (WP) and card detect (CD). WP and CD are both connected to COMM via a mechanical switch inside the socket when a device is inserted.

Three other signals shown on the connector are COMM and the mechanical switches WP and CD. When a device is inserted in the example schematic (Figure 5-1), WP may be and CD is connected to COMM via a mechanical switch inside the socket

SDCard devices have a write protect tab. Depending on the position of the tab, the WP signal may or may not be connected to the COMM signal. Connect the WP signal to a CPLD or other device capable of indicating to the driver software that the card is write protected. In this example, COMM is tied to a VCC and WP has a pull-down resistor. This causes a rising edge when the tab is in the write protect position and the WP signal remains low when the tab is in the read/write position.

The CD signal, MMC_DETECT, indicates to the MMC controller when a card is installed. It is used for both an SDCard socket and an MMC socket. Since the MMC socket does not have the mechanical CD switch, other measures must be taken to produce a card detect. Thus, the SDCard and MMC cases are discussed separately.

Note: While this schematic shows two ways to create a card detect, it is recommended that an SDCard socket be used if a card detect and write protection signal are desired even if only MMC devices are being used.

5.1.2.1SDCard Socket

When using Figure 5-1, “Applications Processor MMC and SDCard Signal Connections” on page 5-3 as a template for your SDCard circuit design, all resistors labeled “DNI IF SD” should not be installed and all resistors labeled “DNI IF MMC” should be installed in the circuit. Removing R226 and inserting R225 causes the VSS2 signal on pin 6 to be tied to ground. Also, the SDCard needs a pull-down resistor in position R228.

SDCard sockets have a card detect switch internal to the socket. The CD signal is physically connected to the COMM signal. Connect the CD signal to a CPLD or other device capable of indicating to the driver software that a card has been inserted in the socket. In this example, COMM is tied to a VCC and CD has a pull-down resistor. This causes a rising edge on CD when a card is inserted while the CD signal remains low if no card is in the socket.

5.1.2.2MMC Socket

When using Figure 5-1, “Applications Processor MMC and SDCard Signal Connections” on page 5-3 as a template for your MMC circuit design, all resistors labeled “DNI IF MMC” should not be installed and all resistors labeled “DNI IF SD” should be installed in the circuit. This causes the VSS2 signal on pin 6 to be pulled-up through resistor R227.

Unlike SDCard sockets, MMC sockets do not have a card detect or write protect switch. In order to implement this, a pull-up is placed on the VSS2 signal (pin 6 of the socket.) Since VSS2 and VSS1 are connected internally on the MMC device, the signal called nMMC_DETECT on the schematic is driven low when the MMC device is inserted.

5-4

PXA250 and PXA210 Applications Processors Design Guide

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Intel PXA250 and PXA210 manual SDCard Socket
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PXA250 and PXA210 specifications

The Intel PXA250 and PXA210 processors, part of the Intel XScale architecture, were introduced in the early 2000s, targeting mobile and embedded applications. They are known for their low power consumption, high performance, and advanced multimedia capabilities, making them suitable for a wide range of devices, including PDAs, smartphones, and other portable computing devices.

The PXA250, which operates at clock speeds ranging from 400 MHz to 624 MHz, features a superscalar architecture that allows it to issue multiple instructions per clock cycle. This enhances the overall performance for demanding applications while maintaining low power usage. It supports a variety of peripheral interfaces, including USB, Ethernet, and various memory types, which contributes to its versatility in different product designs.

One of the key technologies in the PXA250 is the integrated Intel Smart Repeat Technology, which optimizes data processing, thereby reducing the amount of power consumed during operation. This feature is particularly important for battery-powered devices, as it extends the overall battery life, allowing for longer usage times in mobile environments. Additionally, the PXA250 includes a dedicated graphics acceleration unit, which enables enhanced graphics and multimedia performance suited to modern applications at the time.

In contrast, the PXA210 is a more entry-level processor, aimed at cost-sensitive applications. Operating at lower clock speeds, typically around 200 MHz to 400 MHz, it forgoes some of the advanced performance features of the PXA250 while still offering a good balance of performance and power efficiency. The PXA210 is less complex, making it suitable for simpler devices that do not require the extensive capabilities of the PXA250.

Both processors utilize the Intel XScale architecture, which is based on the ARM instruction set. They are built on a 0.13-micron process technology, enabling higher density and lower power consumption compared to their predecessors. With integrated memory controllers and bus interfaces, they facilitate efficient data handling and connectivity options.

In summary, both the Intel PXA250 and PXA210 processors played a crucial role in the evolution of mobile computing by providing powerful processing capabilities with energy efficiency. Their features and technologies enabled device manufacturers to create innovative products that catered to the growing demand for portable devices during that era.
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