The 8-bit microcontrollers P80C557E8, P83C557E8 and P87C557E8 - hereafter referred to as P8xC557E8 - are manufactured in an advanced CMOS process and are derivatives of the 80C51 microcontroller family.
The P8xC557E8 contains a volatile 2048 bytes read/write Data Memory, five 8-bit I/O ports, one 8-bit input port, two 16-bit timer/event counters (identical to the timers of the 80C51), an additional 16-bit timer coupled to capture and compare latches, a 15-source, two-priority-level, nested interrupt structure, an 8-input ADC, a dual Digital-to-Analog Convertor (DAC), Pulse Width Modulated interface, two serial interfaces (UART and I²C-bus), a Watchdog Timer, an on-chip oscillator and timing circuits.
The P8xC557E8 is available in 3 versions:
- P80C557E8: ROMless version
- P83C557E8: containing a non-volatile 64 kbytes mask programmable ROM
- P87C557E8: containing 64 kbytes programmable EPROM/OTP.
The P8xC557E8 is a control-oriented CPU with on-chip Program and Data Memory; it cannot be extended with external Program Memory. It can access up to 64 kbytes of external Data Memory. For systems requiring extra capability, the P8xC557E8 can be expanded using standard TTL compatible memories and peripherals.
In addition, the P8xC557E8 has two software selectable reduced power modes: Idle mode and Power-down mode. The Idle mode freezes the CPU while allowing the RAM, timers, serial ports, and interrupt system to continue functioning. The Power-down mode saves the RAM contents but freezes the oscillator, causing all other chip functions to be inoperative.The Power-down mode can be terminated by an external reset, by the seconds interrupt and by any one of the two external interrupts. <!--see Section 15.3.-->
The device also functions as an arithmetic processor having facilities for both binary and BCD arithmetic as well as bit-handling capabilities. The instruction set of the P8xC557E8 is the same as the 80C51 and consists of over 100 instructions: 49 one-byte, 45 two-byte, and 17 three-byte. With a 16 MHz system clock, 58 pct of the instructions are executed in 0.75 µs and 40 pct in 1.5 µs. Multiply and divide instructions require 3 µs.
Electromagnetic Compatibility (EMC)
Primary attention is paid to the reduction of electromagnetic emission of the microcontroller P8xC557E8. The following features reduce the electromagnetic emission and additionally improve the electromagnetic susceptibility:
- Four digital part supply voltage pins (VDD1 to VDD4) and four digital ground pins (VSS1 to VSS4) are placed as pairs of VDDn and VSSn at two adjacent pins, at each side of the package.
- Separated VDD pins for the internal logic and the port buffers.
- Internal decoupling capacitance improves the EMC radiation behaviour and the EMC immunity.
- External capacitors should be connected across associated VDDn and VSSn pins (i.e. VDD1 and VSS1). Lead length should be as short as possible. Ceramic chip capacitors are recommended (100 nF).
Recommendation on ALE
For applications that require no external memory or temporarily no external memory: the ALE output signal (pulses at a frequency of 1/6 ?fOSC) can be disabled under software control (bit RFI; SFR: PCON.5); if disabled, no ALE pulse will occur. ALE pin will be pulled down internally, switching an external address latch to a quiet state. The MOVX instruction will still toggle ALE (external Data Memory is accessed). ALE will retain its normal HIGH value during Idle mode and a LOW value during Power-down mode while in the ?RFIreduction mode?.
Additionally during internal access (EA = 1) ALE will toggle normally when the address exceeds the internal Program Memory size. During external access (EA = 0) ALE will always toggle normally, whether the flag ?RFI? is set or not.