SMSC USB2250 User Manual

Ultra Fast USB 2.0 Multi-Slot Flash Media Controller

Revision 1.1 (05-29-08)

16

SMSC USB2250/50i/51/51i

Crystal 
Input/External 
Clock Input

XTAL1

(CLKIN)

124

ICLKx

24MHz Crystal or external clock input.

XTAL: This pin can be connected to one 
terminal of the crystal or it can be connected 
to an external 24/48MHz clock when a 
crystal is not used.

The MA[1:0]  pins will be sampled 
while nRESET is asserted, and the 
value will be latched upon nRESET 
negation.  This will determine the 
clock source and value.

Crystal Output

XTAL2

123

OCLKx

24MHz Crystal.
This is the other terminal of the crystal, or it 
is left open when an external clock source is 
used to drive XTAL1(CLKIN).  It may not be 
used to drive any external circuitry other than 
the crystal circuit.

1.8V PLL Power

VDD18PLL

125

This pin is the 1.8V Power for the PLL.

If the internal regulator is enabled, then this 
pin must have a 1.0

μ

F (or greater) ±20% 

(ESR <0.1

Ω) capacitor to VSS.

3.3V Analog 

Power 

VDDA33

128

3.3V Analog Power 

Memory Data 
Bus

MD[7:0]

33
29
30
31
34
35
36
37

I/O12

These signals are used to transfer data 
between the internal CPU and the external 
program memory.

These pins have internal weak pull-
up resistors that are controlled by 
the MD_PU_DIS bit of the 
PWR_MGMT_CTL1 register.

Memory Address 
Bus

MA16

28

O12

These signals address memory locations 
within the external memory.  MA16 is a bit 
generated by the ROM Mapper.

Memory Address 
Bus

MA[15:2]

2
4

107

1

113

24

111

109
106
108

110
112
114
116

O12

These signals address memory locations 
within the external memory.