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Acer 390 Series Service Manual Page 120

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Table 2-8
65555 Pin Functions (continued)
Ball
Pin Name
CRT Interface
U3
HYSNC(CSYNC)
V2
VSYNC
Y3
RED
V4
GREEN
W3
BLUE
W2
RSET
V3
DDC
U4
DATA(GPIO2)
DDC CLK(GPIO3)
Note:
HSYNC, VSYNC, GPIO2, and gpio3 are powered by CVCC and GND. RED, GREEN, BLUE and
RSET are powered by AVCC and AGND.
Power/Ground and Standby Control
U5
AVCC
B3
SVCC
A2
SGND
C4,D5
PVCC
A3, B4
PGND
W1
CVCC
D9, &
IVCC
W12
D14
GND
D7
G17
G4,
P17
2-74
Type
Active
Out
Both
CRT Horizontal Sync (polarity is programmable) or
"Composite Sync" for support of various external
NTSC/PAL encoder chips
Out
Both
CRT Vertical Sync (polarity is programmable)
Out
Analog
CRT analog video outputs from the internal color
Out
Analog
palette DAC. The DAC is designed for a 37.5S2
Out
Analog
equivalent load on each pin (e.g. 75Q resistor on
the board, in parallel with the 75D CRT load)
In
N/A
Set point resistor for the internal color palette DAC.
A 560 Q 1% resistor is required between RSET and
AGND
I/O
High
General purpose I/0, suitable for use as DDC data.
I/O
High
General purpose I/0, suitable for use as DDC
DATA. These two pins are functionally suitable for a
DDC interface between the 65555 and a CRT
monitor
VCC
-
Analog power and ground pins for noise isolation
for the internal color palette DAC. AVCC should be
isolated from digital VCC as described in the
Functional Description of the internal color palette
DAC. For proper DAC operation, AVCC should not
be greater than IVCC. AGND should be common
with digital ground but must be lightly decoupled to
AVCC. See the Functional Description of the
internal color palette DAC for further information
VCC
-
Analog power and ground pins for noise isolation
GND
-
for the internal clock synthesizer (for MCLK). Must
VCC
-
be the same as IVCC, 3.3V.
GND
Analog power and ground pins for noise isolation
for internal clock synthesizer (for VCLK). Must be
the same as IVCC.
SVCC/SGND and PVCC/PGND pairs must be
carefully decoupled individually. Refer also lo the
section on clock ground layout in the Functional
Description.
VCC
Power for CRT Interface, 3.3V.
VCC
-
Power/Ground (Internal Logic), 3.3V. Note that this
voltage must be the same as SVCC and PVCC
GND
-
(voltages for internal clock synthesizers)
Description
Service Guide

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