UPD17217GT datasheet(17/84 Pages) NEC

17 / 84 page

µPD17215, 17216, 17217, 17218

2.4.3

General register (GR)

A general register is a 16-word register on the data memory and used for arithmetic operations and transfer of data to

and from the data memory.

(1)

Configuration of general register

Figure 2-6 shows the configuration of the general register.

A general register occupies 16 nibbles (16 x 4 bits) on a selected row address of the data memory.

The row address is selected by the general register pointer (RP) of the system register. The RP having four

significant bits in the

µPD17217 and 17218 can point to any row address in the range of 0H to 7H of each bank

(BANK0 and BANK1).

In the

µPD17215 and 17216, 3 bits are available in the RP. These bits can point to any row address in the

range of 0H to 7H of BANK0.

(2)

Functions of the general register

The general register enables an arithmetic operation and data transfer between the data memory and a

selected general register by a single instruction. As a general register is a part of the data memory, you can say

that the general register enables arithmetic operation and data transfer between two locations of the data memory.

Similarly, the general register can be accessed by a Data Memory Manipulation instruction as it is a part of the

data memory.

Fig. 2-6 Configuration of General Registers

(RP)

RPH

RPL

b 3 b 2 b 1 b 0 b3 b2 b1 b 0

000

001

010

011

100

101

110

111

000

001

010

011

100

101

110

111

0123456789ABCDE

System registers

Port register

General registers (16 nibbles)

General register pointer

BANK0

BANK1

Column address

General register

settable range

→

System registers

Example:

General registers

when

RP = 0000010B

←

Same system

registers exist

Port

regis-

ter

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