Z86D99 ZILOG [Zilog, Inc.], Z86D99 Datasheet - Page 65

• Manufacturer Part Number: Z86D99
• Description: Low-Voltage Micro controllers with ADC
• Manufacturer: ZILOG [Zilog, Inc.]

PS003807-1002
____3___
_____2__
______1_
_______0
Bit
Bit/Field
R/W
Reset
R = Read, W = Write, X = Indeterminate
Bit
Position
7654_____
_____3210
Table 15. FLAGS Register [Group/Bank F0h, Register C (R252)] (Continued)
Register Pointer (RP)
Z8 instructions can access registers directly or indirectly using either a 4-bit or 8-
bit address field. The upper nibble of the Register Pointer, as described in
Table 16, contains the base address of the active Working Register GROUP. The
lower nibble contains the base address of the Expanded Register File BANK.
When using 4-bit addressing, the 4-bit address of the working register (r0 to rF) is
combined with the upper nibble of the Register Pointer (identifying the WR
GROUP), thus forming the 8-bit actual address.
Table 16. RP Register [Group/Bank F0h, Register D (R253)]
Decimal Adjust
Flag (D)
Half Carry
Flag (H)
User Flag (F2)
User Flag (F1)
7
Working Register Group
R/W
0
Bit/Field
Working Register
Group Pointer
Expanded
Register File
Bank Pointer
P
6
R/W
0
R
E
L
R/W
R/W
R/W
R/W
5
R/W
0
R/W
R/W
R/W
I
M
Z86D990/Z86D991 OTP and Z86L99X ROM
1
0
1
0
1
0
1
0
4
R/W
0
Value
X
X
I
Low-Voltage Microcontrollers with ADC
N
A
Used for BCD arithmetic—after a
subtraction, the flag is set to 1;
following an addition, it is cleared to 0
Set to 1, whenever an addition
generates a “carry out” of bit position
3 (overflow) of an accumulator; or
subtraction generates a “borrow into”
bit 3
User definable
User definable
3
Expanded Register File Bank
R/W
0
Description
Identifies 1 of 16 possible WR
Groups, each containing 16 Working
Registers
Identifies 1 of 16 possible ERF
Banks; only Banks 0, D, and F are
valid for the Z86D99/Z86L99 family
R
Y
2
R/W
0
1
R/W
0
0
R/W
0
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