
MSM80C154S/83C154S¡ Semiconductor
PIN DESCRIPTIONS
Symbol |
| Descriptipn |
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P0.0 to P0.7 | Bidirectional I/O ports. They are also the data/address bus (input/output of data and output of | ||
| lower | ||
| They are | ||
| bus. |
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P1.0 to P1.7 | P1.0 to P1.7 are | ||
| ports. Two of them have the following secondary functions: | ||
| •P1.0 (T2) | : used as external clock input pins for the timer/counter 2. | |
| •P1.1 (T2EX) | : used as trigger input for the timer/counter 2 to be reloaded or captured; | |
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| causing the timer/counter 2 interrupt. | |
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P2.0 to P2.7 | P2.0 to P2.7 are | ||
| an external memory is accessed. They are pulled up internally when used as input ports. | ||
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P3.0 to P3.7 | P3.0 to P3.7 are | ||
| ports. They also have the following secondary functions: | ||
| •P3.0 (RXD) |
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| Serial data input/output in the I/O expansion mode and serial data input in the UART mode when | ||
| the serial port is used. | ||
| •3.1 (TXD) |
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| Synchronous clock output in the I/O expansion mode and serial data output in the UART mode | ||
| when the serial port is used. | ||
| •3.2 (INT0) |
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| Used as input pin for the external interrupt 0, and as | ||
| •3.3 (INT1) |
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| Used as input pin for the external interrupt 1, and as | ||
| •3.4 (T0) |
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| Used as external clock input pin for the timer/counter 0. | ||
| •3.5 (T1) |
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| Used as external clock input pin for the timer/counter 1 and | ||
| •3.6 (WR) |
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| Output of the | ||
| •3.7 (RD) |
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| Output of the | ||
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ALE | Address latch enable output for latching the lower | ||
| Two ALE pulses are activated per machine cycle except during external data memory access at | ||
| which time one ALE pulse is skipped. | ||
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PSEN | Program store enable output which enables the external memory output to the bus during external | ||
| program memory access. Two PSEN pulses are activated per machine cycle except during | ||
| external data memory access at which two PSEN pulses are skipped. | ||
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EA | When EA is held at "H" level, the MSM 83C154S executes instructions from internal program | ||
| memory at address 0000H to 3FFFH, and executes instructions from external program memory | ||
| above address 3FFFH. | ||
| When EA is held at "L" level, the MSM80C154S/MSM83C154S executes instructions from external | ||
| program memory for all addresses. |
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