"The Philips microcontrollers described in this data sheet are high-performance static 80C51 designs incorporating Philips’ high-density CMOS technology with operation from 2.7 V to 5.5 V.
They support both 6-clock and 12-clock operation. The 8xC31X2/51X2 and 8xC32X2/52X2/54X2/58X2 contain 128 byte RAM and 256 byte RAM respectively, 32 I/O lines, three 16-bit counter/timers, a six-source, four-priority level nested interrup structure, a serial I/O port for either multi-processor communications, I/O expansion or full duplex UART, and on-chip
oscillator and clock circuits.

Features:

• 80C51 Central Processing Unit
–4 kbytes ROM/EPROM (80/87C51X2)
–8 kbytes ROM/EPROM (80/87C52X2)
–16 kbytes ROM/EPROM (80/87C54X2)
–32 kbytes ROM/EPROM (80/87C58X2)
–128 byte RAM (80/87C51X2 and 80C31X2)
–256 byte RAM (80/87C52/54X2/58X2 and 80C32X2)
–Boolean processor
–Fully static operation
–Low voltage (2.7 V to 5.5 V at 16 MHz) operation
• 12-clock operation with selectable 6-clock operation
• Memory addressing capability
–64 kbytes ROM and 64 kbytes RAM
• Power control modes:
–Clock can be stopped and resumed
–Idle mode
–Power-down mode
• CMOS and TTL compatible
• Two speed ranges at VCC= 5 V
–0 to 30 MHz with 6-clock operation
–0 to 33 MHz with 12-clock operation

"