Cd Location & Label Storage - Sony CDP-CX235 Training Manual

CD Allocation & Label Storage
Syscon IC501 has its built-in memory to remember if the door was open
or closed, whether the disc was chucked or unchucked, and what order of
songs to play (program play). This information is lost when the CD Changer
is turned OFF. For other items that have to be remembered, IC501 uses
an external static (S-RAM) memory IC502, powered by C522 when the
changer is OFF.
IC502 stores the following information:
•
Keeps track of what tray table slots have discs
•
Stores disc slot number currently in use
•
Groups discs (maximum of eight discs per group)
•
Stores a name for each disc (Label)
•
Logs tracks on a disc to be skipped (not played)
S-RAM Operation
IC502 is an S-Ram that stores bits of data using low power CMOS logic
gates. A one-Farad capacitor, C522, provides power to IC502 when the
CD Changer is turned OFF, preventing the loss of data for up to a month.
When the CD Changer is ON, Syscon IC501 can read or write into each
location of the memory by first enabling IC502 (CE = LOW), addressing a
memory location, selecting read (WE = HIGH) or write (WE = LOW), and
finally reading or writing the information. This S-RAM stores the informa-
tion 8 bits at a time so a single address location reads or writes a Byte of
data (8 bits).
Writing to Memory
The memory writing operation can be seen in the first scope shot. It was
taken as the disc door is closing and the tray is rotating (press the Close
Door button). At this time, every disc slot is being checked for discs as
the tray rotates. If the memory information does not agree with the con-
tents of the disc slot, the memory is rewritten to with the current informa-
tion.
Channel 1 shows that S-RAM IC502 is enabled at power ON. Only one of
the 14 address lines is represented in channel 2. As the tray rotates,
IC501 sends its corresponding address to IC502.
23
P M 3 3 9 4 , F L U K E & P H I L I P S
ch1
1
ch2
ch3
2
ch4
T
3
C H 1 5 . 0 0 V =
C H 2 ! 5 . 0 0 V =
4
C H 3 ! 5 . 0 0 V =
C H 4 ! 5 . 0 0 V = C H P M T B 1 0 . 0 m s - 1 . 6 6 d v c h 3 -
Syscon Checking the Tray for Discs
Channel
1. CE (chip enable - low)
2. 1 of 14 Address lines
3. WE (write enable - low)
4. 1 of 8 Data lines
Time base = 10msec/div
At each address location, the data is read while the write enable line (WE
= Ch 3) is HIGH. This data (Ch 4) is sent to Syscon IC501 for compari-
son. Meanwhile, disc detector Q801 will place a HIGH at IC501/pin 38 if
there is NO disc at that slot location. If the memory also shows there is
NO disc at this location, the two pieces of information agree and there is
no change to the memory data. If they do not, WE goes LOW (Ch 3)
while still at that same address location (Ch 2) and the new data from
IC501/pin 38 is placed into memory.
Reading from Memory
The memory reading operation can be seen in the second scope shot.
This was taken with no disc chucked and the rotary encoder knob turned
to move the tray table. At each tray slot the memory location was read to
see if there is a disc at that slot.
Name IC502/pin
20
27
4
15