DESCRIPTION OF PIN FUNCTIONS
DIP PIN | PLCC PIN | NAME |
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NO. | NO. | SYMBOL |
| DESCRIPTION | |
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| MICROCONTROLLER INTERFACE | |||
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Address | A0/nMUX, | Input. | On a | ||
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| A1,A2/ALE | signals are directly connected to the low bits | ||
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| of the host address bus. On a multiplexed | |
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| address/data bus, A0/nMUX is tied low, A1 | |
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| is left open, and A2 is tied to the Address | |
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| Latch Enable signal of the host. A1 is | |
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| connected to an internal | |
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Data | Input/Output. On a | ||||
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| these signals are used as the data lines for | ||
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| the device. On a multiplexed address/data | |
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| bus, | |
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| (latched by ALE) and as the low data lines | |
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| for the device. | |
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| data only. These signals are connected to | |
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| internal | |
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23 | 27 | nRead/nData | nRD/nDS | Input. | On a |
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| nStrobe |
| signal is issued by the microcontroller as the | |
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| data strobe signal to strobe the data onto | |
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| the bus. On a | |
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| signal is issued by the microcontroller to | |
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| indicate a read operation. In this case, a | |
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| logic "0" on this pin, when the COM20020 is | |
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| accessed, enables data from the device to | |
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| the data bus to be read by the | |
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| microcontroller. | |
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22 | 26 | nWrite/ | nWR/DIR | Input. | On a |
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| Direction |
| issued by the microcontroller as the | |
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| Read/nWrite signal to determine the | |
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| direction of data transfer. In this case, a | |
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| logic "1" selects a read operation, while a | |
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| logic "0" selects a write operation. In this | |
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| case, data is actually strobed by the nDS | |
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| signal. On an | |
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| signal is issued by the microcontroller to | |
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| indicate a write operation. In this case, a | |
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| logic "0" on this pin, when the COM20020 is | |
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| accessed, enables data from the data bus to | |
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| be written to the device. | |
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