SMSC USB2244i User Manual

Ultra Fast USB 2.0 SD/MMC Flash Media Controller

Revision 1.0 (05-27-08)

10

SMSC USB2244/USB2244i

This section provides a detailed description of each signal. The signals are arranged in functional
groups according to their associated interface.

The “n” symbol in the signal name indicates that the active, or asserted, state occurs when the signal
is at a low voltage level. When “n” is not present before the signal name, the signal is asserted at the
high voltage level.

The terms assertion and negation are used exclusively. This is done to avoid confusion when working
with a mixture of “active low” and “active high” signals. The term assert, or assertion, indicates that a
signal is active, independent of whether that level is represented by a high or low voltage. The term
negate, or negation, indicates that a signal is inactive.

SD Data

SD_D[7:0]

7
8

10
20
23
25

4
5

I/O12PU

The bi-directional signals should have weak 
pull-up resistors.  The register can be 
controlled by: SD_MMC_INTF_EN bit of 
SDC_MODE_CTL

SD Clock

SD_CLK 

9

O12

This is an output clock signal to SD/MMC 
device.

The clock frequency is software configurable.

SD Command

SD_CMD

11

I/O12PU

This is a bi-directional signal that connects to 
the CMD signal of SD/MMC device. The bi-
directional signal should have an internal weak 
pull-up resistor.

The pull-up register can be controlled by:
SD_MMC_INTF_EN bit of SDC_MODE CTL

SD Write Protect

SD_nWP

30

I/O12

This pin is designated as the Secure Digital 
card mechanical write detect pin.

SD Card Detect 
GPIO

GPIO15 
(SD_nCD)

26

I/O12

This is a GPIO designated as the Secure 
Digital card detection pin.

USB Bus Data

USB+
USB-

2
3

I/O-U

These pins connect to the USB bus data 
signals. 

USB Transceiver 
Bias

RBIAS

35

I-R

A 12.0k , 1.0% resistor is attached from VSSA 
to this pin in order to set the transceiver's 
internal bias currents.