ARM ARM7TDMI - Page 35

Open Access
Circuit Descriptions
3-19
ARM Development Board (ARM7TDMI Version)
Hardware Reference Guide
ARM DUI 0017C
3.2.12 PC Card Connectors and Power Supply
The PC card connectors and power supply schematic is shown in A.14 PC Card
Connecters and Power Supply
on page A-15.
This schematic shows two voltage switching devices (U26 and U27) and two PC card socket
connectors (SK4A and SK4B). The two socket connectors form one physical device, housing
two card slots. The upper slot is A and the lower slot is B. The connectors are driven directly
from the PC card controller, which is also responsible for determining the card voltage.
To function correctly, the MIC2560 (U26 and U27) requires supplies at +3.3V (VDD),
+5V (VCC), and +12V (VPP). If any of these supplies are not connected, the supply
presented to the card will be incorrect. The card VCC voltage depends upon two inputs,
VCC5EN and VCC3EN. With VCC3EN tied HIGH through a surface mount link (LK12 and
LK13), VCC5EN controls the supply.
The card VPP voltage depends upon two inputs:
Note
The signal names for slot A are prefixed by A_.
The signal names for slot B are prefixed by B_.
Driving this signal LOW sets
the card VCC voltage at +5V.
Driving the signal HIGH puts
the power supply pins into a high
impedance state, effectively cutting
off the supply to the card.
VG-468 signal name
MIC2560-1 signal name
nVCCEN
VCC5EN
-
VCC3EN
VCC Supply5V 0 1
HIGH Z 1 1
•EN0
•EN1
By driving these signals HIGH and
LOW the supply can be switched
between +5V, +12V, GND and high
impedance. See the table on the
right for more information.
VG-468 signal name
MIC2560-1 signal name
VPP1EN
EN1
VPP2EN
EN2
VPP Supply0V 0 0
5V 0 1
12V 1 0
HIGH Z 1 1
hrg.book Page 19 Wednesday, July 22, 1998 9:18 AM