DESCRIPTION OF PIN FUNCTIONS
PIN NO. | NAME | SYMBOL | TYPE | DESCRIPTION |
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26 |
| MIDLEN1 | O4 | Powerdown output to modem controller. This |
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| pin is active (high) when either the PWRDWN |
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| bit (CSR bit 2) is set or the modem is disabled |
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| (not configured). |
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20 | Modem Ring | MRINGIN | I | Ring input from the modem controller. |
| Input |
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| Toggles when ringing, low when not ringing. |
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21 | nModem | nMRINGOA | O4 | Ring output signal. When there is no ringing |
| Ring Output |
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| on the MRINGIN pin and the modem is not in |
| A |
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| Powerdown mode this output is high. During |
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| ringing this signal is the inverse of the |
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| MRINGIN input. When the PWRDWN bit is |
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| set or the function is disabled, this output is |
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| low. This signal is activated about 12 msec |
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| after removing Powerdown. |
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22 | Modem Ring | MRINGOB | O4 | Ring output signal. When the modem is not in |
| Output B |
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| Powerdown mode (PWRDWN bit is zero and |
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| the function is enabled) this output follows the |
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| value of the MRINGIN input. When entering |
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| Powerdown mode, a rising edge is generated |
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| on the pin. A rising edge is also generated |
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| when exiting Powerdown mode also. Refer to |
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| Figure 2. |
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14 | Speaker | SPKRIN | I with pullup | Speaker Input. This is a digitized (single level) |
| Input |
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| audio input from the modem controller. |
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15 | Speaker | SPKROUT | O4 | Speaker Output. This pin reflects the SPKRIN |
| Output |
| with pullup | pin when enabled by the AUDIO bit (Modem |
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| CSR bit 3). When disabled this pin is tri- |
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| stated. |
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28 |
| nMPDOUT | I Schmitt | Used to control Powerdown mode. Tie to a |
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| 180K |
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| Tie high when not used. This signal is used |
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| in the RC time constant. |
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29 |
| MFBK1 | O4 with | Tie to nMPDOUT through a 5.1M resistor. |
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| pullup | This signal is used in the RC time constant |
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| in conjuction with the nMPDOUT pin. |
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| 13 |
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