Initial Sled Motor Drive
Initial Sled Movement
Start
When the laser’s platform is lifted to a level position, the disc is sand- wiched between the spindle motor table and the magnet. In this position the disc is said to be “chucked”. The chucked position requires System Control IC202 to retrieve the initial sled program stored in EEProm memory IC201 (not shown) via the parallel bus.
Movement
The program in IC201 instructs the sled motor to move the laser to home position then quickly outward, but the sled does not stop. It just slows down while the laser and focus search is activated. If a disc is found, the sled stops and playback begins. However, if no disc is found, the sled speeds up and moves outward again further into the disc area. As it slows down a second time, the laser and focus system is instructed to look for a disc (specifically its information layer). If it fails to find it, the sled is quickly moved outward the last time for the third search. The “no disc found” cycle concludes when the sled motor is reversed and the laser assembly is driven home.
ICs Used
System Control IC202 controls the sled motor during this initial disc search stage. A series of ICs are used for this control:
·System Control IC202 uses HGA IC601 as an expansion port
·HGA IC601 instructs Servo DSP IC701
·Servo DSP IC701 issues analog commands to Driver IC802
·Sled Driver IC802 sends voltages to the stepper sled motor
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IC202 employs expansion port Hybrid Gate Array (HGA) IC601 for assis- tance in managing the remaining ICs.
IC202 to IC601 Communications
When IC202 wants to send data to IC601, IC202 must also send chip select, clock, write pulses and address information to support the data.
IC202 to IC601 Communications Signals
Signal | Active | Signal Present When: |
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Chip Select (CS1 or CS4 | Low | IC202 & IC205 gets Vcc |
from IC202/pins 10 or 7)) |
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Clock IC202/pin 5 | Low | IC202 gets B+ |
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Write IC202/pin 22 | Low | IC202 & IC205 gets Vcc |
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Six Address lines HA |
| IC202 gets B+ |
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16 Data lines HD |
| IC202 gets B+ |
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IC601 to IC202 Communications
When IC601 wants to send reply data to IC202, an interrupt signal is sent to IC202. When IC202 is ready, it will send chip select, clock, read pulses, and address to support the data received from IC601.
IC601 to IC202 Communications
Signal | Active | Signal Present When: |
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Interrupt (INT1 or INT3) | Low | An operation is completed |
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| (e.g. sled moved) |
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Chip Select (CS1 or CS4) | Low | IC202 & IC205 gets Vcc |
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Clock IC202/pin 5 | Low | IC202 gets B+ |
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Read IC202/pin 24 | Low | IC202 & IC205 gets Vcc |
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Six Address lines HA |
| IC202 gets B+ |
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16 Data lines HD |
| IC202 gets B+ |
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System Control IC202 uses HGA IC601
System Control IC202 plans out the DVD operations, but turns the details of each operation over to a partner IC. It is much like a manager who starts many projects, but has the details of each project finished by a subordinate. When there are too many projects, the manager needs help from an assistant manager to help oversee the activity. System Controls
HGA IC601 Instructs Servo DSP IC701
IC601 controls many ICs. One of them is Servo DSP IC701. Communi- cations between these ICs use four control lines to transfer the address and data on the parallel bus: