LC78681E Datasheet, PDF (17/23 Pages) Sanyo Semicon Device – Digital Signal Processor for Compact Disc Players

LC78681E
Notes: 1. The WRQ pin normally indicates Q subcode standby status, but provides different information during the Track Count mode or internal braking.
(See the sections on track counting and internal braking.)
2. The LC78681E is active when CS is low, with output from SQOUT. SQOUT is in the high-impedance state when the CS pin is high.
Reading Level Meter (LVM) and Peak Meter (PKM) Data
MSB
LSB
00101011
00101100
00101101
00101110
Command
PKM set (LVM reset)
LVM set (PKM reset)
PKM mask set
PKM mask reset
RES = low
1. Level Meter (LVM)
• The Level Meter mode is enabled by inputting the Level Meter Set command (2CH).
• Level meter data is 16 bits, and is composed of 15 bits of absolute-value data and an MSB indicating left-right
polarity. Data is for the left channel when the MSB is high and for the right channel when low.
• Level meter data is appended at the end of 80 bits of Q subcode data, and can be read from the SQOUT pin by
clocking the CQCK pin 96 times. The left and right channels are swapped each time that level meter data is read. The
left and right channels are independent, and the highest value read for each of the channels is held.
2. Peak Meter (PKM)
• The Peak Meter mode is enabled by inputting the Peak Meter Set command (2BH).
• Peak meter data is 16 bits, and is composed of 15 bits of absolute-value data and an MSB fixed at 0. The maximum
value is detected with no regard for right or left channel.
• Peak meter data is read in a manner similar to that for level meter data. However, data is not updated by further
reading.
• The absolute time for Q subcode data when in the Peak Meter mode is issued while holding the absolute time
(ATIME) that is detected after generation of the maximum value. (Relative time is normal operation.)
• Issuing a Peak Meter Mask Set command causes values larger than the maximum value already in memory to be
ignored, even when this command is issued in the Peak Meter mode. This is canceled by the Peak Meter Mask Reset
command (used in peak searches for songs in memory).
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