Zilog Z8F0130 Manuel d'utilisateur télécharger pdf (Page 20)

eZ8

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CPU Core

User Manual

UM012820-0810 Architectural Overview

(256 byte boundary) of the Register File. The Stack Pointer Register val-

ues are undefined after Reset.

The Register Pointer contains address information for the current Work-

ing Register Group and the Register File Page. The Page Pointer is the

lower 4-bits of the Register Pointer, RP[3:0], and points to the current

Page. There are sixteen 256-byte Pages available. The Working Register

Group Pointer is the upper 4 bits of the Register Pointer, RP[7:4], and

points to one of sixteen 16-byte Working Register Groups. There are 16

Working Register Groups per page. For more information on the Register

File, see Address Space on page 17.

Flags Register

The Flags Register contains the status information regarding the most

recent arithmetic, logical, bit manipulation or rotate and shift operation.

The Flags Register contains six bits of status information that are set or

cleared by CPU operations. Four of the bits (C, V, Z, and S) can be tested

with conditional jump instructions. Two flags (H and D) cannot be tested

and are used for Binary-Coded Decimal (BCD) arithmetic.

The two remaining bits, User Flags (F1 and F2), are available as general-

purpose status bits. User Flags are unaffected by arithmetic operations

and must be set or cleared by instructions. The User Flags cannot be used

with conditional Jumps. They are undefined at initial power-up and are

unaffected by Reset. Figure 2 on page 6 displays the flags and their bit

positions in the Flags Register.

1 2 ... 15 16 17 18 19 20 21 22 23 24 25 ... 313 314

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Zilog Z8F0130 Manuel d'utilisateur Page 20