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87C652 Datasheet(PDF) 7 Page - NXP Semiconductors |
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87C652 Datasheet(HTML) 7 Page - NXP Semiconductors |
7 / 24 page Philips Semiconductors Product specification 87C652/87C654 80C51 8-bit microcontroller 8K/16K, 256 OTP, I2C 1999 Jul 23 7 OSCILLATOR CHARACTERISTICS XTAL1 and XTAL2 are the input and output, respectively, of an inverting amplifier. The pins can be configured for use as an on-chip oscillator, as shown in the Logic Symbol. To drive the device from an external clock source, XTAL1 should be driven while XTAL2 is left unconnected. There are no requirements on the duty cycle of the external clock signal, because the input to the internal clock circuitry is through a divide-by-two flip-flop. However, minimum and maximum high and low times specified in the data sheet must be observed. Reset A reset is accomplished by holding the RST pin high for at least two machine cycles (24 oscillator periods), while the oscillator is running. To insure a good power-on reset, the RST pin must be high long enough to allow the oscillator time to start up (normally a few milliseconds) plus two machine cycles. At power-on, the voltage on VCC and RST must come up at the same time for a proper start-up. Idle Mode In the idle mode, the CPU puts itself to sleep while all of the on-chip peripherals stay active. The instruction to invoke the idle mode is the last instruction executed in the normal operating mode before the idle mode is activated. The CPU contents, the on-chip RAM, and all of the special function registers remain intact during this mode. The idle mode can be terminated either by any enabled interrupt (at which time the process is picked up at the interrupt service routine and continued), or by a hardware reset which starts the processor in the same manner as a power-on reset. Power-Down Mode In the power-down mode, the oscillator is stopped and the instruction to invoke power-down is the last instruction executed. Only the contents of the on-chip RAM are preserved. A hardware reset is the only way to terminate the power-down mode. The control bits for the reduced power modes are in the special function register PCON. Table 2 shows the state of the I/O ports during low current operating modes. I2C SERIAL COMMUNICATION—SIO1 The I2C serial port is identical to the I2C serial port on the 8XC552. The operation of this subsystem is described in detail in the 8XC552 section of this manual. Note that in both the 8XC652/4 and the 8XC552 the I2C pins are alternate functions to port pins P1.6 and P1.7. Because of this, P1.6 and P1.7 on these parts do not have a pull-up structure as found on the 80C51. Therefore P1.6 and P1.7 have open drain outputs on the 8XC652/4. Table 2. External Pin Status During Idle and Power-Down Mode MODE PROGRAM MEMORY ALE PSEN PORT 0 PORT 1 PORT 2 PORT 3 Idle Internal 1 1 Data Data Data Data Idle External 1 1 Float Data Address Data Power-down Internal 0 0 Data Data Data Data Power-down External 0 0 Float Data Data Data Serial Control Register (S1CON) – See Table 3 S1CON (D8H) CR2 ENS1 STA STO SI AA CR1 CR0 Bits CR0, CR1 and CR2 determine the serial clock frequency that is generated in the master mode of operation. Table 3. Serial Clock Rates BIT FREQUENCY (kHz) AT fOSC CR2 CR1 CR0 6 MHZ 12 MHz 16 MHz 20 MHz fOSC DIVIDED BY 0 0 0 23 47 62.5 78 256 0 0 1 27 54 71 891 224 0 1 0 31.25 62.5 83.3 1041 192 0 1 1 37 75 100 1251 160 1 0 0 6.25 12.5 17 21 960 1 0 1 50 100 1331 1661 120 1 1 0 100 2001 2671 3341 60 1 1 1 0.25 < 62.5 0 to 255 0.5 < 62.5 0 to 254 0.65 < 55.6 0 to 253 0.81 < 69.4 0 to 253 96 × (256 – (reload value Timer 1)) (Reload value range: 0 – 254 in mode 2) NOTE: 1. These frequencies exceed the upper limit of 100kHz of the I2C-bus specification and cannot be used in an I2C-bus application. |
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