47C101M 데이터 시트보기 (PDF) - Toshiba

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47C101M

CMOS 4-bit Microcontroller

Toshiba 

TMP47C101/201

2. Internal CPU Function

2.1 Program Counter (PC)

The program counter is a 11-bit binary counter which indicates

the address of the program memory storing the next instruc-

tion to be executed.Normally, the PC is incremented by the

number of bytes of the instruction every time it is fetched.

When a branch instruction or a subroutine instruction has been

executed or an interrupt has been accepted, the specified val-

ues listed in Table 2-1 are set to the PC. The PC is initialized to

“0” during reset.

Figure 2-1. Configuration of Program Counter

The PC can directly address a 2048-byte address space.

However, with the short branch, the following points must be

considered:

• Short branch instruction [BSS a]

In [BSS a] instruction execution, when the branch con-

dition is satisfied, the value specified in the instruction

is set to the lower 6 bits of the PC.That is, [BSS a]

becomes the in-page branch instruction. When [BSS

a] is stored at the last address of the page, the upper 5

bits of the PC point the next page, so that branch is

made to the next page.

Table 2-1 Status Change of Program Counter

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