DS87C550

The DS87C550 EPROM High-Speed Microcontroller with ADC and PWM is a member of the fastest 100% 8051-compatible microcontroller family available. It features a redesigned processor core that removes wasted clock and memory cycles. As a result, it executes 8051 instructions up to three times faster than the original architecture for the same crystal speed. The DS87C550 also offers a maximum crystal speed of 33MHz, resulting in apparent execution speeds of up to 99MHz.

The DS87C550 uses an industry standard 8051 pin-out and includes standard resources such as three timer/counters, and 256 bytes of scratchpad RAM. This device also features 8kB of EPROM with an extra 1kB of data RAM (in addition to the 256 bytes of scratchpad RAM), and 55 I/O ports pins. Both One-Time-Programmable (OTP) and windowed packages are available.

Besides greater speed, the DS87C550 includes a second full hardware serial port, seven additional interrupts, a programmable watchdog timer, brownout monitor, and power-fail reset.

The DS87C550 also provides dual data pointers (DPTRs) to speed block data memory moves. The user can also dynamically adjust the speed of external accesses between two and 12 machine cycles for flexibility in selecting memory and peripherals.

Power Management Mode (PMM) is useful for portable or battery-powered applications. This feature allows software to select a lower speed clock as the main time base. While normal operation has a machine cycle rate of 4 clocks per cycle, the PMM allows the processor to run at 1024 clocks per cycle. For example, at 12MHz, standard operation has a machine cycle rate of 3MHz. In Power Management Mode, software can select an 11.7 kHz (12MHz/1024) machine cycle rate. There is a corresponding reduction in power consumption due to the processor running slower.

The DS87C550 also offers two features that can significantly reduce electromagnetic interference (EMI).One EMI reduction feature allows software to select a reduced emission mode that disables the ALE signal when it is unneeded. The other EMI reduction feature controls the current to the address and data pins interfacing to external devices producing a controlled transition of these signals.

Designers using the DS87C550 as an upgrade for the 87C552 or similar 8051-based microcontrollers with A/D capability should read Application Note 2: The DS87C550 as an Upgrade for 8051 Derivatives.