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參數(shù)資料
| 型號： | SI2439-A-GM |
| 廠商： | Silicon Laboratories Inc |
| 文件頁數(shù)： | 17/70頁 |
| 文件大小： | 0K |
| 描述： | IC ISOMODEM 33.6KBPS 38-QFN |
| 標(biāo)準(zhǔn)包裝： | 364 |
| 系列： | * |
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Si2494/39
24
Rev. 1.0
Figure 9. Loop Current
4.17. Overcurrent Detection
The Si2494/39 includes an overcurrent detection feature that measures the loop current at a programmable time
after the Si2494/39 goes off-hook. This allows the Si2494/39 to detect if it is connected to an improper telephone
line. The overcurrent detection feature may be enabled by setting the OCDM bit (U70, bit 11). OHT (U77, bits 8:0)
sets the delay after off-hook until the loop current is measured. See “AN93: ISOmodem Chipset Family Designer's
Guide” for details.
4.18. Global Operation
The Si2494/39 chipset contains an integrated silicon direct access arrangement (Silicon DAA) that provides a
programmable line interface to meet international telephone line interface requirements. “AN93: Modem Designer’s
Guide” gives the DAA register settings required to meet international PTT standards.
Additionally, the user-access registers (via the AT:U and AT:R commands) may be programmed for country-specific
settings, such as dial tone, ring, ringback, and busy tone. See AN93 for complete details.
4.19. Firmware Upgrades
The Si2494/39 contains an on-chip program ROM that includes the firmware required for the features listed in this
data sheet. In addition, the Si2494/39 contains on-chip program RAM to accommodate minor changes to the ROM
firmware. This allows Silicon Labs to provide future firmware updates to optimize the characteristics of new modem
designs and those already deployed in the field. See AN93 for complete details.
4.20. DTMF Detection / Generation
The Si2494/39 provides comprehensive DTMF tone generation and detection. The ISOmodem can generate
single tones or DTMF tones using the +VTS command. DTMF tones may also be generated during dialing using
the “ATDT” command. DTMF detection is only available in voice mode (FCLASS = 8). DTMF digits are reported
from the modem to the host using <DLE> shielding.
0 3 6 9 12 15 18 21 24
30 33 36 39 42 45 48 51 54 57 60 63 66 69 72
140
75 78 81 84 87 90 93
Loop Current
(mA)
LVCS
BITS
27
Overload
0
5
10
15
20
25
30
CTR21 only
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| SI2439-A-GMR | 制造商:Silicon Laboratories Inc 功能描述:33.6 KBPS ISOMODEM + VOICE - Tape and Reel 制造商:Silicon Laboratories Inc 功能描述:IC ISOMODEM 33.6KBPS 38-QFN |
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