Faultfinding Guide
GB 55CDR779 8.
8. Faultfinding Guide
8.1 Display Board
8.1.1 Description of display board
General description
The display board has three major parts : the FTD
(Fluorescent Tube Display), the display controller
TMP87C874F and the keyboard. The display controller is
controlled by the DASP master processor on the CDR main
board. The communication protocol used is I2C. So all the
information between DASP and display controller goes via
the SDA or I2C DATA and SCL or I2C CLK lines.
Communication is always initiated by the DASP on the CDR
main board. Unlike the previous generations of CDR players,
the interrupt generated by the display controller at key-press
or reception of remote control is not used. Instead, the DASP
polls the display controller for these events.
Display controller TMP87C874F
TMP87C874F (IC7104) is a high speed and high
performance 8-bit single chip microprocessor, containing 8-
bit A/D conversion inputs and a VFT (Vacuum Fluorescent
Tube) driver. In this application, its functions are :
• slave microprocessor.
• FTD driver.
• generates the square wave for the filament voltage
required for an AC FTD.
• generates the grid and segment scanning for the FTD.
• generates the scanning grid for the key matrix.
• input for remote control.
All the communication runs via the serial bus interface I2C.
The display controller uses an 8MHz resonator as clock
driver.
Figure 8-1
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TMP87C874F
SCL
SDA
VSS1
XOUT
XIN
RESETN
P22
P21
TEST1
P20
INT0
INT1
SCK0
PORT3
I C
2
VKK
COUNTER
PROGRAM
I/O PORT1
TIMER/COUNTER
I/O PORT6 (VFT)
VASS
VAREF
VDD
I/O PORT8 (VFT)
CONVERT.
8 BIT A/D
16 BIT
( RAM )
512X8 BIT
DATA MEMORY
TIMER/COUNTER
( ROM )
8kX8 BIT
INTERRUPT
CONTROLLER
I/O PORT7 (VFT)
( I/O PORT2 )
PROGR MEMORY
I/O PORT0
CLOCK/TIMING CONTROLLER
8 BIT
I/O PORTD (VFT) I/O PORT9 (VFT)
I/O PORT5
I/O PORT4
C P U
INT0 external interrupt input 0
INT1 external interrupt input 1
RESETN reset signal input, active low
SCL I2C-bus serial clock input/output
SDA I2C-bus serial data input/output
TEST test pin, tied to low
VAREF analog reference voltage input
VASS analog reference ground
VDD +5V
VKK VFT driver power supply
VSS ground
XIN, XOUT resonator connecting pins for high-frequency clock
BLOCK DIAGRAM
PIN DESCRIPTIONS
CL 96532076_028.eps
290799
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