Host Interface Signals
The host interface signals are described in the table below.
Pin# |
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| TTL RS232 |
| USB |
| Description |
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| Input: TTL RS232 polarity control with 32k ohm |
1 |
| 232INV | NC |
| Connect to ground for UART to UART signal polarity. | ||
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| Pull up to Vin for standard TTL RS232 polarity. |
2 |
|
| Vin |
| Vin |
| Power: Supply voltage input (3V to 5.5V) |
3 |
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| GND |
| GND |
| Ground: Power and signal ground. |
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| Input: TTL Level RS232 Receive data input, weak pull up to Vin. |
4 |
| (n)RxD | D- |
| Polarity determined by Pin1 | ||
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| Bidirectional: USB D- Signal |
5 |
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| (n)TxD |
| <reserved> |
| Output: TTL Level RS232 transmits data. Polarity Determined |
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| by Pin 1 | |||
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| Input: TTL level Clear to Send, weak pull up to Vin. Polarity |
6 |
| (n)CTS |
| D+ |
| configurable via software | |
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| Bidirectional: USB D+ signal |
7 |
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| (n)RTS |
| <reserved> |
| Output: TTL level RS232 Request to Send. Polarity |
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| configurable via software | |||
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8 |
| PWRDWN | PWRDWN |
| Output: Open drain, 100K pull up to Vin; active high indicates | ||
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| that the IS4920 is in Power Down Mode. | |||||
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9 |
| nBEEPER | nBEEPER |
| Output: Open drain, 100K pull up to Vin; active low signal | ||
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| capable of sinking current. PWM controlled signal can | |||||
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| be used to drive an external beeper. |
10 |
| nGoodRead |
| nGoodRead |
| Output: Open drain, 100K pull up to Vin; active low signal for | |
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| sinking current of a Good Read LED circuit. | ||||
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11 |
| nWAKE |
| nWake |
| Input: Weak pull up to Vin; active low, the signal can be used to | |
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| bring the engine out of Power Down (TTL RS232 version | ||||
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| only) or Sleep Mode (TTL RS232 and USB versions). |
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12 |
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| nTrig |
| nTrig |
| Input: Weak pull up to Vin; active low, the signal can be used as |
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| a trigger input to activate the IS4920. | |||
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17