No. 6015-21/31

LC78622NE

18. Interpolation Circuit

Outputting incorrect audio data that could not be corrected by the error detection and correction circuit would result

in loud noises being output. To minimize this noise, the LC78622NE replaces the incorrect data with linearly

interpolated data based on the correct data on either side of the incorrect data. If one set of C2 flags indicate errors,

the above replacement is performed, and if two or more sets of C2 flags indicate errors, the IC holds the previous

value. However, when correct data is output following two or more consecutive C2 flags indicating errors, the data

point between the correct data and the data output two points previously (the held value) is replaced with a value

computed by linearly interpolating those two values.

19. General-Purpose I/O Ports; Pin 24: CONT1, Pin 25: CONT2, Pin 26: CONT3, Pin 27: CONT4, Pin 28: CONT5, Pin

29: EMPH/CONT6, Pin 34: PCCL, Pin 35: MUTEL/CONT7, Pin 42: MUTER/CONT8

The LC78622NE provides five I/O ports CONT1 to CONT5 and three output ports CONT6 to CONT8. After a reset,

these five I/O ports are set to function as input pins and the three output ports are set to function as EMPH, MUTEL,

and MUTER pins, respectively. Unused I/O ports must be connected to ground set to function as input ports or set to

function as output ports.

The port information can be read out from the SQOUT pin in synchronization with the falling edge of the CQCK

signal in the order CONT1 to CONT5 by using the PORT READ command. When the pin WRQ enters ‘H’ level by

the subcode Q output while controlling general-purpose port, the data for the subcode Q should be invalid and

another subcode Q should be read out. This command has the 1-byte command format. Command control limited to

only the general-purpose ports is possible by using the PCCL pin setting, even during track check, track jump, and

internal MTR braking operations. When using the general-purpose port command control function during track

check and similar operations, set the PCCL pin high and input the desired general-purpose I/O ports commands

(codes $D9 through $DF). (Only the general-purpose I/O port commands are accepted when the PCCL pin is high.)

The PCCL pin must be set low to input a command other than a general-purpose I/O port command. However, if a

track check or other command is applied when the PCCL pin is at the low level, the operation that is being performed

will be interrupted. The state of the PCCL pin must only be changed when the RWC pin is low. However, it must not

be changed during subcode Q readout.

Note: When track checking, if the same number of desired tracks as general-purpose I/O port commands (codes

$D9 to $DF) is applied to with the PCCL held at ‘L’ level, general-purpose port command as well as track count

operation for desired track count will be executed. Therefore, the desired tarack count data should not be set to the

codes $D9 to $DF with the PCCL held at ‘L’ level when track checking.

Code

Command

RES = low

$DD

PORT READ

$DB

PORT I/O SET

PORT I SET

$DC

PORT OUTPUT SET

$D9

Enable the CONT6 function

$DA

Enable the EMPH function

q

q

$DE

Enable the CONT7 and CONT8 functions

$DF

Enable the MUTEL and MUTER functions

q

q