SM5905AF datasheet(23/35 Pages) NPC

23 / 35 page

NIPPON PRECISION CIRCUITS-23

SM5905AF

Fig 2. YBLKCK and VWA relationship

The VWA is determined according to the YBLKCK

pin and WAQV command. Refer to the timing chart

below.

1.YBLKCK is a 75 Hz clock(HIGH for 136

µs) when

used for normal read mode and it is a 150 Hz clock

when used for double-speed read mode, synchro-

nized to the CD format block end timing.

When this clock goes LOW, WA which is the write

address of internal encode sequence, is stored

(see note 2).

2.The microcontroller checks the subcode and, if

confirmed to be correct, generates a WAQV com-

mand (80H).

3.When the WAQV command is received, the previ-

ously latched WA is stored as the VWA.

(note 2) Actually, there is a small time difference, or

gap, between the input data and YBLKCK. This gap

serves to preserves the preceding WA to protect

against incorrect operation.

RAM addresses

The SM5905AF has a 4M DRAM as the internal

buffer and an external 4M DRAM can be also con-

nected to expand the memory to 4M bits.

Three kinds of addresses are used for external

RAM control.

WA (write address)

RA (read address)

VWA (valid write address)

Among these, VWA is the write address for con-

forming data whose validity has been confirmed.

Determination of the correctness of data read from

the CD is delayed relative to the encode write pro-

cessing, so VWA is always delayed relative to WA.

The region available for valid data is the area

between VWA-RA.

- Connect data work area

This is an area of memory reserved for connect

data. This area is 4k bits.

Fig 1. RAM addresses

VWA

Valid data

area

Connect data work area

VWA (valid write address)

13.3ms

VWA latch set

WAQV set

VWA(x)

VWA(x + 1)

YBLKCK

Microcontroller data set

Refer to Microcontroller interface

VWA

Values shown are for rate fs. The values are 1/2 those shown at rate 2fs.

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