HD404816FS datasheet(72/100 Pages) RENESAS

72 / 100 page

HD404818 Series

Programmable ROM Operation

The MCU on-chip PROM is programmed in PROM mode. PROM mode is set by pulling

TEST, M

0, and

1 low, and RESET high, as shown in figure 38. In PROM mode, the MCU does not operate. It can be

programmed like a standard 27256 EPROM using a standard PROM programmer and an 80-to-28-pin

socket adapter. Table 31 lists the recommended PROM programmers and socket adapters.

Since an instruction of the HMCS400 series consists of 10 bits, the HMCS400 series microcomputer

incorporates a conversion circuit to enable the use of a general-purpose PROM programmer. By this circuit,

an instruction is read or programmed using two addresses, a lower 5 bits and upper 5 bits. For example, if 8

kwords of on-chip PROM are programmed by a general-purpose PROM pro-grammer, 16 kbytes of

addresses ($0000–$3FFF) should be specified.

Programming and Verification

The MCU can be programmed at high speed without causing voltage stress or affecting data reliability.

Table 30 shows how programming and verification modes are selected.

Precautions

1. Addresses $0000 to $3FFF must be specified if the PROM is programmed by a PROM programmer. If

addresses of $4000 or higher are accessed, the PROM may not be programmed or verified. Note that

plastic package types cannot be erased and reprogrammed. Data in unused addresses must be set to $FF.

2. Ensure that the PROM programmer, socket adapter, and LSI match. Using the wrong programmer for

the socket adapter may cause an overvoltage and damage the LSI. Make sure that the LSI is firmly fixed

in the socket adapter, and that the socket adapter is firmly fixed onto the programmer.

3. The PROM should be programmed with V

PP = 12.5 V. Other PROMs use 21 V. If 21 V is applied to the

MCU, the LSI may be permanently damaged. 12.5 V is the Intel 27256 setting.

Table 30 PROM Mode Selection

Mode

0–O7

Programming

Low

High

Data input

Verify

High

Low

Data output

Programming inhibited

High

High impedance

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