SM5859AF Nippon Precision Circuits Inc, SM5859AF Datasheet - Page 22

• Manufacturer Part Number: SM5859AF
• Description: compression and non compression type antishock memory controller
• Manufacturer: Nippon Precision Circuits Inc

RAM addresses
The SM5859 uses either 1 or 2 external 1M or 4M
DRAMs as external buffers.
Three kinds of addresses are used for external
RAM control.
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
VWA (valid write address)
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) when used for
normal read mode and it is a 150Hz clock when
used for double-speed read mode. Both modes
clock are synchronized 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).
This is an area of memory reserved for connect
data. This area is 2Kbits if using 1M DRAMs, or
4Kbits if using 4M DRAMs.
WA (write address)
RA (read address)
VWA (valid write address)
Refer to Microcontroller interface
Microcontroller data set
YBLKCK
VWA
Fig 2. YBLKCK and VWA relationship
Values shown are for rate fs. The values are 1/2 those shown at rate 2fs.
VWA(x)
SM5859AF
VWA latch set
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, VWA is
updated according to the previously latched WA.
(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.
WAQV set
13.3ms
VWA
VWA(x + 1)
WA
Fig1. RAM addresses
NIPPON PRECISION CIRCUITS-22
Connect data work area
Valid data
area
RA