HD404654 Datasheet, PDF (88/109 Pages) Hitachi Semiconductor – 4-Bit Single-Chip Microcomputer

HD404654 Series
Programming the Built-In PROM
The MCU’s built-in PROM is programmed in PROM mode. PROM mode is set by pulling TEST, M₀, and
M₁ low, and RESET low as shown in figure 74. In PROM mode, the MCU does not operate, but it can be
programmed in the same way as any other commercial 27256-type EPROM using a standard PROM
programmer and a 42-to-28-pin socket adapter. Recommended PROM programmers and socket adapters
of the HD4074654 are listed in table 28.
Since an HMCS400-series instruction is ten bits long, the HMCS400-series MCU has a built-in conversion
circuit to enable the use of a general- purpose PROM programmer. This circuit splits each instruction into
five lower bits and five upper bits that are read from or written to consecutive addresses. This means that
if, for example, 4 kwords of built-in PROM are to be programmed by a general-purpose PROM
programmer, an 8 kbyte address space ($0000–$7FFF) must be specified.
Warnings
1. Always specify addresses $0000 to $1FFF when programming with a PROM programmer. If address
$2000 or higher is accessed, the PROM may not be programmed or verified correctly. Set all data in
unused addresses to $FF.
Note that the plastic-package version cannot be erased or reprogrammed.
2. Make sure that the PROM programmer, socket adapter, and LSI are aligned correctly (their pin 1
positions match), otherwise overcurrents may damage the LSI. Before starting programming, make
sure that the LSI is firmly fixed in the socket adapter and the socket adapter is firmly fixed onto the
programmer.
3. PROM programmers have two voltages (V_PP): 12.5 V and 21 V. Remember that ZTAT™ devices
require a V_PP of 12.5 V—the 21-V setting will damage them. 12.5 V is the Intel 27256 setting.
Programming and Verification
The built-in PROM of the MCU can be programmed at high speed without risk of voltage stress or damage
to data reliability.
Programming and verification modes are selected as listed in table 27.
For details of PROM programming, refer to the preface section, Notes on PROM Programming.
Table 27 PROM Mode Selection
Pin
Mode
CE
OE
V_PP
Programming
Low
High
V_PP
Verification
High
Low
V_PP
Programming inhibited
High
High
V_PP
O₀–O₇
Data input
Data output
High impedance
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