Datasheet

DS87C520/DS83C520 EPROM/ROM High-Speed Microcontrollers
4 of 43
Figure 1. Block Diagram
PIN DESCRIPTION
PIN
DIP PLCC TQFP
NAME FUNCTION
40 44 38 V
CC
Positive Supply Voltage. +5V
20 1, 22, 23 16, 17, 39 GND
Digital Circuit Ground
9 10 4 RST
Reset Input. The RST input pin contains a Schmitt voltage input
to recognize external active high Reset inputs. The pin also
employs an internal pulldown resistor to allow for a combination
of wired OR external reset sources. An RC is not required for
power-up, as the device provides this function internally.
18 20 14 XTAL2
19 21 15 XTAL1
Crystal Oscillator Pins. XTAL1 and XTAL2 provide support for
parallel-resonant, AT-cut crystals. XTAL1 acts also as an input if
there is an external clock source in place of a crystal. XTAL2
serves as the output of the crystal amplifier.
29 32 26 PSEN
Program Store-Enable Output. This active-low signal is
commonly connected to optional external ROM memory as a chip
enable. PSEN provides an active-low pulse and is driven high
when external ROM is not being accessed.
DS87C520/
DS83C520