DS87C530/DS83C530 EPROM/ROM Microcontrollers with
Table 6. PMM Control and Status Bit Summary
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| FUNCTION | RESET | WRITE ACCESS | |||||
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| 0 to 1 only when | |||
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| EXIF.3 | Control. XT/ RG =1, runs from crystal or external |
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XT/ RG | X | XTUP = 1 and | |||||||||||
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clock; XT/ RG =0, runs from internal ring oscillator. | |||||||||||||
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| XTOFF= 0 | ||||||||
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RGMD | EXIF.2 | Status. RGMD=1, CPU clock = ring; RGMD = 0, | 0 | None | |||||||||
CPU clock = crystal. | |||||||||||||
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| Control. CD1, 0 = 01, 4 clocks; CS1, 0 = 10, PMM1; |
| Write CD1, 0 = 10 or | |||||||
CD1, CD0 | PMR7, PMR.6 | 0, 1 | 11 only from CD1, 0 = | ||||||||||
CD1, 0 = 11, PMM2. | |||||||||||||
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| 01 |
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SWB | PMR.5 | Control. SWB = 1, hardware invokes switchback to 4 | 0 | Unrestricted | |||||||||
clocks, SWB = 0, no hardware switchback. | |||||||||||||
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| Control. Disables crystal operation after ring is |
| 1 only when XT/ |
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XTOFF | PMR.3 | 0 | RG | ||||||||||
selected. | = 0 |
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PIP | STATUS.7 | Status. 1 indicates a | 0 | None | |||||||||
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HIP | STATUS.6 | Status. 1 indicates high priority interrupt in service. | 0 | None | |||||||||
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LIP | STATUS.5 | Status. 1 indicates low priority interrupt in service. | 0 | None | |||||||||
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XTUP | STATUS.4 | Status. 1 indicates that the crystal has stabilized. | 1 | None | |||||||||
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SPTA1 | STATUS.3 | Status. Serial transmission on serial port 1. | 0 | None | |||||||||
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SPRA1 | STATUS.2 | Status. Serial word reception on serial port 1. | 0 | None | |||||||||
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SPTA0 | STATUS.1 | Status. Serial transmission on serial port 0. | 0 | None | |||||||||
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SPRA0 | STATUS.0 | Status. Serial word reception on serial port 0. | 0 | None | |||||||||
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