UPD750108(A) データシートの表示（PDF） - NEC => Renesas Technology

部品番号

コンポーネント説明

メーカー

UPD750108(A)

4 BIT SINGLE-CHIP MICROCONTROLLER

NEC => Renesas Technology 

µPD750104, 750106, 750108, 750104(A), 750106(A), 750108(A)

4. Mk Ι MODE/Mk ΙΙ MODE SWITCH FUNCTION

4.1 Differences between Mk Ι Mode and Mk ΙΙ Mode

The CPU of the µPD750108 has two modes (Mk Ι mode and Mk ΙΙ mode) and which mode is used is selectable.

Bit 3 of the stack bank selection register (SBS) determines the mode.

• Mk Ι mode:

• Mk ΙΙ mode:

This mode has the upward compatibility with the 75X series.

It can be used in the 75XL CPUs having a ROM of up to 16 KB.

This mode is not compatible with the 75X series.

It can be used in all 75XL CPUs, including those having a ROM of 16 KB or more.

Table 4-1 shows the differences between Mk Ι mode and Mk ΙΙ mode.

Table 4-1. Differences between Mk Ι Mode and Mk ΙΙ Mode

Number of stack bytes in a

subroutine instruction

BRA !addr1 instruction

CALLA !addr1 instruction

CALL !addr instruction

CALLF !faddr instruction

Mk Ι mode

2 bytes

None

3 machine cycles

2 machine cycles

Mk ΙΙ mode

3 bytes

Available

4 machine cycles

3 machine cycles

Caution Mk ΙΙ mode can be used to support a program area larger than 16K bytes in the 75X series or 75XL

series. This mode enhances a software compatibility with products whose program area is larger

than 16K bytes. If Mk ΙΙ mode is selected, when the subroutine call instruction is executed, the

number of stack bytes (use area) will be increased by one byte for each stack, compared to Mk

Ι mode. When a CALL !addr or CALLF !faddr instruction is executed, it takes one more machine

cycle. Therefore, Mk Ι mode should be used for applications for which RAM efficiency or

processing capabilities is more critical than a software compatibility.

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