3. TECHNICAL BRIEF
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3.11.2.4 Secure digital (SD)
Secure digital (SD) products are flash-based memory cards specifically designed to meet the security, capacity,
performance, and environmental requirements of popular audio and video consumer devices. Their physical
form factors, pin assignments, and data transfer protocols are forward-compatible with the multimedia card
(MMC), but with higher bandwidth, copyright protection (via secure version), and functional expansion through
secure data input/output (SDIO) capability. SDIO enables external devices to communicate with a host like the
MSM8x55 IC through its SD interface. An example MSM device SDIO application is 802.11 WLAN support.
The MSM8x55 IC provides up to three SD interfaces (Table 7-1) that provide:
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Clock output up to 52 MHz
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2.85 V operation on SDC4; 1.8 V operation on SDC1, SDC2, and SDC3
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SDIO compatible WLAN (802.11)
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Interface with SD/MMC memory cards up to 32 GB
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Internal 10 k to 100 k pull-up resistors on the command and data pins
3.11.3 Keypad interface
The PMIC GPIOs can be configured to support a keypad matrix up to 18 rows by 8 columns (18 × 8). One set of
pins is connected to the keypad’s columns and is used for sensing; another set is connected to the keypad’s rows
and is used for driving. The sensed columns reveal when any keypad button is pressed, and then the rows are
driven sequentially to determine precisely which keypad button was pressed.
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