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μPD556 (EVACHIP-43) - NEC
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Manufacturer NEC
Model Number EVACHIP-43
Part Number μPD556, μPD556B
Introduction 1977 (launch)
General information
Family μCOM-43
Clock 150 kHz-440 kHz
Microarchitecture μCOM-43
Technology pMOS
Word size 4 bit
0.5 octets
1 nibbles
Op. Temp -10 °C – 70 °C
Supply VDD -10 V
Supply VSS 0 V
RAM 48 B
4.8e-5 MB
0.048 kB
384 b
4.8e-8 GB
(96x4 bit)
Max Addressable Memory 2 kB
Stack 3 levels
Pins 64
IRQ lines 2
I/O ports 35
Package QIL64 (QIL), CerQIL64 (CerQIL)

The μPD556 or EVACHIP-43 is a 4-bit evaluation/development microcontroller used for both software and hardware debugging of the μPD546 microcontroller. Since the μCOM-43 is a strict superset of the μCOM-44 and μCOM-45, this evaluation chip was also used for debugging those two those chip families as well.

The 556 is functionally identical to the μPD546 without the internal memory, which instead is needed to be supplied externally and connected via the additional pins. This chip also has a HOLD operation that allows step-by-step inspection of operations.


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Instruction Set[edit]

Main article: μCOM-4 ISA
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  • NEC Microcomputers, Inc., 1980 Catalog, "μCOM-43/44/45 4-Bit Single Chip Microcomputers, μPD556 EVACHIP-43", 153-156 pp.
  • NEC Electronics (Europe) GmbH, 1982 Catalog, "μPD556B μCOM-4 4-Bit Single Chip ROM-less Evaluation Chip", 173-176 pp.

See also[edit]

familyμCOM-43 +
first launched1977 +
full page namenec/μcom-43/μpd556 +
instance ofmicrocontroller +
manufacturerNEC +
max operating temperature70 °C +
microarchitectureμCOM-43 +
min operating temperature-10 °C +
model numberEVACHIP-43 +
packageQIL64 + and CerQIL64 +
part numberμPD556 + and μPD556B +
pin count64 +
ram4.8e-5 MB (0.048 kB, 48 B, 384 b, 4.8e-8 GB) +
ram breakdown96x4 bit +
technologypMOS +
word size4 bit (0.5 octets, 1 nibbles) +