Zilog Z8F0130 - Manual (Page 20)

eZ8
™
CPU Core
User Manual
UM012820-0810 Architectural Overview
5
(256 byte boundary) of the Register File. The Stack Pointer Register val-
ues are undefined after Reset.
Register Pointer
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.