Sharp FACSIMILE FO-4500 Service Manual page 94

FO-4500H
(2) Image memory block
This block is composed of 2 MByte flash memory and 128 KByte
SRAM.
1) LH28F800SUT (IC6) --- Pin-56, TSOP
The memory is a non-volatile type whose content does not volatilize
even if power is turned off, and stores the copied, sent and received
image data. Moreover, the initially registered data, registered content
of "RELAY" key and registered content of "CONF" key are stored.
2) M5M5255CFP (IC3, 8) -- pin-32, SOP
(256 Kbit SRAM)
The setting of receiving mode, optional setting content, soft switch
content and dairy data are stored. Even if the power supply of the
main body is turned off, it is backed up with lithium.
(3) Modem block
The block is mainly composed of the modem R144EFXL (IC4), and is
provided with the following modem function.
Commu-
Modu-
nication Baud rate lation
No.
mode
system
14400 128-value
bps
1 G3
TCM
12000 64-value
2 G3
TCM
9600 16-value
3 G3
QAM
7200 8-phase
4 G3
PSK
4800 8-phase
5 G3
PSK
2400 4-phase
6 G3
PSK
300 FSK
7 G3
AM•PM•
8 G2
VSB
In addition to the above functions, the following tone transfer/tone
detection functions are also provided.
No. Signal name Frequency
1 CED 2100Hz
2 G1 1850
3 GC 2100
4 CFR 1650
5 MCF 1650
6 LCS 1100
7 EOM 1100
8 PIS 462
ITU-T
Transmis-
Modu-
sion recom-
lation rate
mendation
frequency
2400baud 1800Hz V33, V17
2400 1800 V33, V17
2400 1700 V29, V17
2400 1700 V29
1600 1800 V27ter
1200 1800 V27ter
300 1650/ V21
1850
2100 T3
No. Signal name Frequency
1 G1 1850Hz
2 CFR,MCF 1650
3 GC 2100
The above functions are controlled by getting an access to the inter-
face memory in the modem through the data bus from CPU (IC12) of
the control PWB. The interface memory is composed of 32 8-bit regis-
ters, and is controlled with the bank switch. Accordingly, the register is
selected by the register selection signals (RS4 to RS0) of 5 bits and
chip selection signal (CS). The major content controlled by these reg-
isters is as follows.
1) Configuration register
Mode setting of V17, V29, V27, G2, FSK and tone transmission
2) Option register
Equalizing method of equalizer, carrier detection threshold, addition of
echo suppressor protect tone, and setting of transmission/reception
mode
3) Others
G2AGC control, tone frequency setting, and so on
Moreover, data is read from these registers through the data bus to
monitor the statuses of the modem such as tone detection, training
pattern detection and so on.
Next, transmission/reception operation is described.
During sending, the sent data is given from the control block to the
modem through the data bus. Then, it is modulated and sent to LIU
PWB with SIGTX signal. During receiving, the received data is sent
from LIU PWB to the modem with SIGRX signal and is demodulated.
Then, it is sent to the control block with the data bus. The above
operation is done with the modem LSI (IC).
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