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S87L51FA-7F40 Datasheet(PDF) 5 Page - NXP Semiconductors |
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S87L51FA-7F40 Datasheet(HTML) 5 Page - NXP Semiconductors |
5 / 16 page Philips Semiconductors Product specification 87L51FA/87L51FB CMOS single-chip 3.0V 8-bit microcontrollers 1996 Aug 16 3-154 PIN DESCRIPTIONS (Continued) PIN NUMBER MNEMONIC DIP LCC QFP TYPE NAME AND FUNCTION P3.0–P3.7 10–17 11, 13–19 5, 7–13 I/O Port 3: Port 3 is an 8-bit bidirectional I/O port with internal pull-ups. Port 3 pins that have 1s written to them are pulled high by the internal pull-ups and can be used as inputs. As inputs, port 3 pins that are externally being pulled low will source current because of the pull-ups. (See DC Electrical Characteristics: IIL). Port 3 also serves the special features of the 80C51 family, as listed below: 10 11 5 I RxD (P3.0): Serial input port 11 13 7 O TxD (P3.1): Serial output port 12 14 8 I INT0 (P3.2): External interrupt 13 15 9 I INT1 (P3.3): External interrupt 14 16 10 I T0 (P3.4): Timer 0 external input 15 17 11 I T1 (P3.5): Timer 1 external input 16 18 12 O WR (P3.6): External data memory write strobe 17 19 13 O RD (P3.7): External data memory read strobe RST 9 10 4 I Reset: A high on this pin for two machine cycles while the oscillator is running, resets the device. An internal diffused resistor to VSS permits a power-on reset using only an external capacitor to VCC. ALE/PROG 30 33 27 I/O Address Latch Enable/Program Pulse: Output pulse for latching the low byte of the address during an access to external memory. In normal operation, ALE is emitted at a constant rate of 1/6 the oscillator frequency, and can be used for external timing or clocking. Note that one ALE pulse is skipped during each access to external data memory. This pin is also the program pulse input (PROG) during EPROM programming. PSEN 29 32 26 O Program Store Enable: The read strobe to external program memory. When the 87L51FA/FB is executing code from the external program memory, PSEN is activated twice each machine cycle, except that two PSEN activations are skipped during each access to external data memory. PSEN is not activated during fetches from internal program memory. EA/VPP 31 35 29 I External Access Enable/Programming Supply Voltage: EA must be externally held low to enable the device to fetch code from external program memory locations 0000H and 1FFFH. If EA is held high, the device executes from internal program memory unless the program counter contains an address greater than 1FFFH. This pin also receives the 12.75V programming supply voltage (VPP) during EPROM programming. If security bit 1 is programmed, EA will be internally latched on Reset. XTAL1 19 21 15 I Crystal 1: Input to the inverting oscillator amplifier and input to the internal clock generator circuits. XTAL2 18 20 14 O Crystal 2: Output from the inverting oscillator amplifier. NOTE: To avoid “latch-up” effect at power-on, the voltage on any pin at any time must not be higher than VCC + 0.5V or VSS – 0.5V, respectively. TIMER 2 This is a 16-bit up or down counter, which can be operated as either a timer or event counter. It can be operated in one of three different modes (autoreload, capture or as the baud rate generator for the UART). In the autoreload mode the Timer can be set to count up or down by setting or clearing the bit DCEN in the T2CON Special Function Register. The SFR’s RCAP2H and RCAP2L are used to reload the Timer upon overflow or a 1-to-0 transition on the T2EX input (P1.1). In the Capture mode Timer 2 can either set TF2 and generate an interrupt or capture its value. To capture Timer 2 in response to a 1-to-0 transition on the T2EX input, the EXEN2 bit in the T2CON must be set. Timer 2 is then captured in SFR’s RCAP2H and RCAP2L. As the baud rate generator, Timer 2 is selected by setting TCLK and/or RCLK in T2CON. As the baud rate generator Timer 2 is incremented at 1/2 the oscillator frequency. ENHANCED UART The 87L51FA/FB UART has all of the capabilities of the standard 80C51 UART plus Framing Error Detection and Automatic Address Recognition. As in the 80C51, all four modes of operation are supported as well as the 9th bit in modes 2 and 3 that can be used to facilitate multiprocessor communication. The Framing Error Detection allows the UART to look for missing stop bits. If a Stop bit is missing, the FE bit in the SCON SFR is set. The FE bit can be checked after each transmission to detect communication errors. The FE bit can only be cleared by software and is not affected by a valid stop bit. Automatic Address Recognition is used to reduce the CPU service time for the serial port. The CPU only needs to service the UART when it is addressed and, with this done by the on-chip circuitry, the need for software overhead is greatly reduced. This mode works similar to the 9-bit communication mode, except that it uses only 8 bits and the Stop bit is used to cause the RI bit to be set. There are two SFRs associated with this mode. They are SADDR, which holds the slave address and SADEN, which contains a mask that allows selective masking of the slave address so that broadcast addresses can be used. |
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