- 您現(xiàn)在的位置：買賣IC網(wǎng) > PDF目錄371754 > FX579 Half Duplex GMSK Modem PDF資料下載
參數(shù)資料
| 型號： | FX579 |
| 英文描述： | Half Duplex GMSK Modem |
| 中文描述： | 半雙工GMSK調(diào)制解調(diào)器 |
| 文件頁數(shù)： | 12/23頁 |
| 文件大?。?/td> | 582K |
| 代理商： | FX579 |
Half Duplex GMSK Modem
FX579
1996 Consumer Microcircuits Limited
12
D/579/4
Acquire Sequence
Figure 7 shows the typical received output from a radio's frequency discriminator. A data transmission
in general begins with a burst of unmodulated carrier followed by preamble of, for example "11001100--
" and then frame sync, so as to allow the receive modem to establish timing and level lock as soon as
possible, before the message is sent.
In most applications there will also be a dc step in the output voltage from the receiver FM discriminator
due to carrier frequency offsets as channels are changed or when the distant transmitter is turned on.
Figure 7 shows two possible receive operating modes of the FX579. The mode shown in (a) is
preferred and should be used when an external carrier detect signal is available, so as to provide the
fastest possible acquisition of the received signal. The mode in (b) is suggested for when a carrier
detect signal is unavailable. The receive operating modes are determined by the logic state of the
ACQUIRE pin as explained in Table 3.
(a)
Operation with a carrier detect (Preferred operating mode)
When an external carrier detect signal is available the μController should provide an ACQUIRE
pulse as shown. The ACQUIRE input is pulsed to a logic "1" a minimum of 2 bit times after the
carrier is detected (to allow for the receive filter delay) and just before preamble is expected (to
reduce the probability of false frame sync detection under noisy conditions). The level
measurement DOC capacitors are then automatically clamped to the input signal for fast
acquisition. The ACQUIRE input should remain at a logic "1" for a minimum of 16 bit times to
enable the level measurement circuits to stabilise and the PLL to quickly achieve lock. The
ACQUIRE input should then be taken to a logic "0" again, for better signal to noise
performance, once the preamble or Frame Sync has been detected by the controlling
microprocessor.
(b)
Suggested operation without a carrier detect (Non-preferred operating mode)
When a carrier detect signal is not available, it is suggested that the modem be operated in the
Lossy Peak Detect/Wide Bandwidth mode (ACQUIRE pin at a logic "1") until the system
μController satisfactorily detects preamble and/or frame sync. Then the ACQUIRE pin should
be taken to a logic "0" for Peak Averaging/Narrow Bandwidth mode, so as to provide a better
signal to noise performance for the rest of the message. The duration of initial unmodulated
carrier plus preamble should be a minimum of 100 bit times to allow the voltages on the
external DOC capacitors to stabilise. At the end of the message the ACQUIRE pin should be
returned to a logic "1".
The FX579 generally can tolerate dc offsets in the received signal of at least ±0.5V with respect to
V
BIAS
(V
DD
= 5V). The voltages on the DOC1 and DOC2 pins reflect the average peak positive and
negative excursions of the (filtered) received signal, and could therefore be used to derive a measure
of the data signal amplitude and carrier frequency offset. Note, however, that these pins are driven
from very high impedance circuits, so that the dc load presented by any external circuitry should
exceed 10M
to V
BIAS
.
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| FX601A | Monostable Multivibrator |
| FX601R | Analog IC |
| FX601 | Ultrahigh-Speed Switching Applications |
| FX6A-20S-0.8SV | 0.8mm Pitch Stacking Height 5 to 9mm Connector |
| FX6-100S-0.8SV | 0.8mm Pitch Stacking Height 5 to 9mm Connector |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| FX579D4 | 制造商:CMLMICRO 制造商全稱:CML Microcircuits 功能描述:HALF DUPLEX GMSK MODEM |
| FX5800-TD | 制造商:Micro-Star International 功能描述:GF FX 5800 128MB 8X AGP - Bulk |
| FX5-80P-SH | 功能描述:CONN HEADER 80POS 1MM R/A GOLD RoHS:否 類別:連接器，互連式 >> 板對板 - 陣列，邊緣類型，包廂 系列:FX5 標(biāo)準(zhǔn)包裝:3,000 系列:SlimStack™ 502396 連接器類型:插頭，外罩觸點(diǎn) 位置數(shù):100 間距:0.016"（0.40mm） 行數(shù):2 安裝類型:表面貼裝 特點(diǎn):固定焊尾 觸點(diǎn)表面涂層:金 觸點(diǎn)涂層厚度:8µin（0.20µm） 包裝:帶卷 (TR) 配接層疊高度:2.5mm 板上方高度:0.084"（2.13mm） 其它名稱:502396-1010 |
| FX5-80P-SH(71) | 功能描述:板對板與夾層連接器 HDR 80P 1MM R/A GOLD RoHS:否 制造商:JAE Electronics 系列:WP3 產(chǎn)品類型:Receptacles 節(jié)距:0.4 mm 疊放高度:1 mm 安裝角: 位置/觸點(diǎn)數(shù)量:50 排數(shù):2 外殼材料:Plastic 觸點(diǎn)材料:Copper Alloy 觸點(diǎn)電鍍:Gold 電壓額定值:50 V 電流額定值:0.4 A |
| FX5-80P-SH(72) | 功能描述:板對板與夾層連接器 80P R/A SMT HEADER LOC BOSS GLD PLT RoHS:否 制造商:JAE Electronics 系列:WP3 產(chǎn)品類型:Receptacles 節(jié)距:0.4 mm 疊放高度:1 mm 安裝角: 位置/觸點(diǎn)數(shù)量:50 排數(shù):2 外殼材料:Plastic 觸點(diǎn)材料:Copper Alloy 觸點(diǎn)電鍍:Gold 電壓額定值:50 V 電流額定值:0.4 A |
發(fā)布緊急采購，3分鐘左右您將得到回復(fù)。