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| VN808资料 | |
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VN808 PDF Download |
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File Size : 116 KB
Manufacturer:STM Description:Port 2, Output. Port 2 serves as the MSB for external addressing. P2.7 is A15 and P2.0 is A8. The device will automatically place the MSB of an address on P2 for external ROM and RAM access. Although Port 2 can be accessed like an ordinary I/O port, the value stored on the Port 2 latch will never be seen on the pins (due to memory access). Therefore, writing to Port 2 in software is only useful for the instructions MOVX A, @Ri or MOVX @Ri, A. These instructions use the Port 2 internal latch to supply the external address MSB. In this case, the Port 2 latch value will be supplied as the address information. Port 3, Input/Output. Port 3 functions as both an 8-bit, bidirectional I/O port and an alternate functional interface for External Interrupts, Serial Port 0, Timer 0 & 1 Inputs, RD and WR strobes. The reset condition of Port 3 is with all bits at logic 1. In this state, a weak pullup holds the port high. This condition also serves as an input mode, since any external circuit that writes to the port will overcome the weak pullup. When software writes a 0 to any port pin, the device will activate a strong pulldown that remains on until either a 1 is written or a reset occurs. Writing a 1 after the port has been at 0 will cause a strong transition driver to turn on, followed by a weaker sustaining pullup. Once the momentary strong driver turns off, the port once again becomes both the output high and input state. The alternate modes of Port 3 are outlined below: |
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| 1PCS | 100PCS | 1K | 10K | ||
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型 号：VN808 厂 家：STM 封 装： 批 号：08+ 数 量：2700 说 明：全新原装，长期稳定供应 |
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运 费： 所在地： 新旧程度： |
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| 联系人：林小姐 |
| 电 话：086-755-23815997 |
| 手 机：13632589437 |
| QQ：1097182423,2851921558 |
| MSN： |
| 传 真：0755-23815984 |
| EMail：joylin@hongbotong.com |
| 公司地址： 深圳市福田区深南中路3006号佳和大厦B座2007室 |
