Functional Description
The HT8658/HT8659 are single chip LSIs with
an external DRAM (dynamic random access
memory). They are designed for applications on
recording sounds. The recording length is de-
cided by the data rate along with the size of an
external memory. The type as well as amount of
DRAM, operation mode and sampling rate are
determined by the connection of the AS0~AS6
pins. The HT8658/8659 provide 2 audio out-
puts. One is filtered by an internal low pass
filter for the sake of improving sound quality in
addition to minimizing external required com-
ponents. The other is non-filtered and a voice
signal can be filtered with an external circuit to
decide the audio cut-off frequency as well as
band width. The two chips have the same func-
tions except the reset time as shown:
Name
R eset Time (Minimum)
HT8658
4 seconds
HT8659
2 seconds
Initial setting of operation mode
The HT8658/HT8659 load the statuses of the
AS0~AS6 pins into a mode register after power
is initially turned on or the system is reset.
These pins are internally built with pull-high
resistors so that all inputs with “1” are the
default value of the mode register. E xternal
pull-low resistors which are tied to the AS0~
AS6 pins defines the operation mode of the ICs
as shown in the following table:
AS0
AS1
AS2
AS3
AS4
AS5
AS6
F unction Description
0
1
1
0
0
0
1
1
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Data rate: 32K bps
Data rate: 22K bps
Data rate: 16K bps
Data rate: 11K bps
X
X
X
X
X
X
X
X
0
1
0
1
0
0
1
1
X
X
X
X
X
X
X
X
X
X
X
X
DRAM chip number: 4 pcs
DRAM chip number: 3 pcs
DRAM chip number: 2 pcs
DRAM chip number: 1 pcs
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
1
0
1
0
X
X
X
X
1
1
0
0
Operation mode: Normal mode
Operation mode: Auto play back mode
Operation mode: Not applicable
Operation mode: Not applicable
X
X
X
X
X
X
X
X
X
X
1
0
X
X
DRAM type: 256Kb
DRAM type: 1Mb
Notes: 1.“0” connects an external pull-low resistor to ASn, where n=0~6.
2.“1” connects no external pull-low resistor to ASn, where n=0~6.
3.“X” means don’t car.
HT8658/HT8659
5
26th Sep ’96