UPD784020 Datasheet, PDF (6/90 Pages) NEC – 16/8-BIT SINGLE-CHIP MICROCOMPUTER

mPD784020, 784021
H 1. DIFFERENCES BETWEEN mPD784026 SUB-SERIES
The only difference between the mPD784020, mPD784021, mPD784025, and mPD784026 is their capacity of
internal memory, port functions, and part of their packages.
The mPD78P4026 is produced by replacing the masked ROM in the mPD784025 or mPD784026 with 64K-byte one-
time PROM or EPROM. Table 1-1 shows the differences between these products.
Table 1-1 Differences between the mPD784026 Sub-Series
Item
Product
mPD784020
mPD784021
mPD784025
mPD784026
mPD78P4026
Internal ROM
None
48K bytes
(masked ROM)
64K bytes
(masked ROM)
64K bytes
(one-time PROM
or EPROM)
Internal RAM
512 bytes
2048 bytes
P40-P47
Functions only as an address/data bus
Can be switched to a general-purpose port or address/data
bus, by using software
P50-P57
P60-P63
Functions only as an address bus
Can be switched to an output-only port
or address bus in units of 2 bits, by
using software
Can be switched to a general-purpose port or address bus in
units of 2 bits, by using software
P64, P65
Functions only as the RD or WR pin
Functions as the RD or WR pin when the local bus interface
is used. Functions as a general-purpose port in other cases.
Package
80-pin plastic QFP 80-pin plastic QFP 80-pin plastic QFP (14 ¥ 14 mm)
(14 ¥ 14 mm)
(14 ¥ 14 mm)
80-pin plastic QFP
(14 ¥ 14 mm)
80-pin plastic
TQFP (fine pitch)
(12 ¥ 12 mm)
80-pin ceramic
WQFN
(14 ¥ 14 mm)
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