DS83C520_07 Datasheet, PDF (4/43 Pages) Dallas Semiconductor – EPROM/ROM High-Speed Microcontrollers

Figure 1. Block Diagram
DS87C520/DS83C520 EPROM/ROM High-Speed Microcontrollers
DS87C520/
DS83C520
PIN DESCRIPTION
PIN
DIP
PLCC
TQFP
40
44
38
20
1, 22, 23 16, 17, 39
9
10
4
18
20
14
19
21
15
29
32
26
NAME
V_CC
GND
RST
XTAL2
XTAL1
PSEN
FUNCTION
Positive Supply Voltage. +5V
Digital Circuit Ground
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.
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.
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.
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