UPD17P133CS datasheet(84/289 Pages) NEC

84 / 289 page

CHAPTER 8 GENERAL REGISTER (GR)

The general register (GR) is allocated in data memory. It can therefore be used directly in performing arithmetic/

logical operations with and in transferring data to and from general data memory.

8.1 GENERAL REGISTER CONFIGURATION

Figure 8-1 shows the configuration of the general register.

As shown in Figure 8-1, sixteen nibbles in a single row address in data memory (16

× 4 bits) are used as the general

The general register pointer (RP) in the system register is used to indicate which row address is to be used as

the general register. Because the RP effectively has three valid bits, the data memory row addresses in which the

general register can be allocated are address locations 0H to 7H. However, note that addresses 40H to 6EH are

uninstalled memory locations and should therefore not be specified as locations for the general register.

8.2 FUNCTIONS OF THE GENERAL REGISTER

The general register can be used in transferring data to and from data memory within an instruction. It can also

be used in performing arithmetic/logical operations with data memory within an instruction. In effect, since the

general register is data memory, this just means that operations such as arithmetic/logical operations and data transfer

can be performed on and between locations in data memory. In addition, because the general register is allocated

in data memory, it can be controlled in the same manner as other areas in data memory through the use of data

memory manipulation instructions.

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