HT8658 Datasheet, PDF (6/15 Pages) Holtek Semiconductor Inc – Voice Recorder (DRAM)

HT8658/HT8659
Recording capacity
The HT8658/HT8659 offer 4 kinds of voice sam-
pling rate, namely 32K, 22K, 16K and 11Kbps
(based on a system frequency of 384KHz), se-
lectable by the connection of the AS0 and AS1
pins. The voice sampling rate decides the re-
cording capacity of the ICs in addition to the
type and amount of DRAM. A higher sampling
rate results in sounds of better quality but
shortens the recording time.
Sampling DRAM Size
Rate
(Maximum)
Recording
Time
32K bps
1Mb×3
94 seconds
22K bps
1Mb×3
136 seconds
16K bps
1Mb×3
188 seconds
11K bps
1Mb×3
272 seconds
Recording Time
Memory selection
The HT8658/HT8659 provide a DRAM inter-
face circuit. The type as well as amount of
DRAM decides the recording length of the ICs
at a designated sampling rate. There are 2
kinds of DRAM, namely 256Kb and 1Mb, select-
able by the connection of the AS5 pin. The ICs
can interface with a maximum of 4 DRAMs for
the 256Kb type but 3 DRAMs for the 1Mb type.
The amount of DRAMs is decided by the connec-
tion of the AS2 and AS3 pins.
AS5 AS3 AS2
Memory Size
1 11
256Kb×1
1 10
256Kb×2
1 01
256Kb×3
1 00
256Kb×4
0 11
1Mb×1
0 10
1Mb×2
0 01
1Mb×3
0 00
1Mb×3
Notes: 1. “0” connects an external pull-low
resistor to ASn, where n=2,3, or 5.
2. “1” connects no external pull-low
resistors to ASn, where n=2, 3 or 5.
Record function
The HT8658/HT8659 enter the recording state
from the standby state when the memories are
not full and the REC key is triggered as well. In
the recording state, sounds input from an exter-
nal microphone are coded by an internal ADM
(adaptive delta modulation) algorithm and
saved in an external memory until the memo-
ries are all full or the REC key is retriggered.
During recording, recording will pause and the
recording counter stop counting by retriggering
the REC key. At this time, if the memories are
not full and the REC key is triggered again, the
ICs will record sounds from the pause position.
Once the memories are full, recording will be
terminated and any retrigger to the REC key be
ignored.
After recording is stopped, the HT8658/HT8659
will play back the recorded sounds automat-
ically in the AUTO PLAY mode. They, on the
other hand, will play back the recorded sounds
by manually triggering the PLAY key in the
normal mode.
Play function
The HT8658/HT8659 provide 2 kinds of playing
modes, namely normal mode and AUTO PLAY
mode. In the normal mode, the ICs will play
back the recorded sounds when recording is
terminated and the PLAY key is triggered. In
the AUTO PLAY mode, they will play back the
recorded sounds automatically without manu-
ally triggering the PLAY key once recording is
terminated. In the process of playing sounds,
triggering the PLAY key will pause the playing
back in addition to the playing counter. To re-
sume playing back, simply retrigger the PLAY
key. Playing back will start at the pause posi-
tion.
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26th Sep ’96