ZiLOG Z8 User Manual

Z8 Microcontrollers
Address Space ZiLOG
2-6 UM001601-0803
2.3 Z8 EXPANDED REGISTER FILE (Continued)
defined for ERF Bank C and ERF Bank F (Table 2-4). All other
working register groups in ERF Banks C and F, as well as the re
-
maining thirteen ERF Banks, are not implemented. All are re-
served for future use.
When an ERF Bank is selected, register addresses 00H to 0FH
access those sixteen ERF Bank registers – in effect replacing the
first sixteen locations of the Z8 Standard Register File.
For example, if ERF Bank C is selected, the Z8 Standard Regis-
ters 00H through 0FH are no longer accessible. Registers 00H
through 0FH are now the 16 registers from ERF Bank C, Work
-
ing Register Group 0. No other Z8 Standard Registers are effect-
ed since only Working Register Group 0 is implemented in ERF
Bank C.
Access to the ERF is accomplished through the Register Pointer
(FDH). The lower nibble of the Register Pointer determines the
ERF Bank while the upper nibble determines the Working Reg
-
ister Group within the register file (Figure 2-6).
The value of the lower nibble in the Register Pointer (FDH) cor-
responds to the ERF Bank identification. Table 2.3 shows the
lower nibble value and the register file assigned to it.
Figure 2-6. Register Pointer (FDH) Example
0 1 1 1
1 1 0 0
Working
Select ERF Bank C(H)
Register
Group
Expanded
Register
Bank
Working Register Group 7(H)
Tab le 2-3. ERF Bank Address
Register Pointer
(FDH)
Low Nibble Hex Register File
0000(B) 0 Z8 Standard Register File *
0001(B) 1 Expanded Register File Bank 1
0010(B) 2 Expanded Register File Bank 2
0011(B) 3 Expanded Register File Bank 3
0100(B) 4 Expanded Register File Bank 4
0101(B) 5 Expanded Register File Bank 5
0110(B) 6 Expanded Register File Bank 6
0111(B) 7 Expanded Register File Bank 7
1000(B) 8 Expanded Register File Bank 8
1001(B) 9 Expanded Register File Bank 9
1010(B) A Expanded Register File Bank A
1011(B) B Expanded Register File Bank B
1100(B) C Expanded Register File Bank C
1101(B) D Expanded Register File Bank D
1110(B) E Expanded Register File Bank E
1111(B) F Expanded Register File Bank F
Note: The Z8 Standard Register File is equivalent to Expanded Reg-
ister File Bank 0.

ZiLOG Z8 Specifications

General

Brand	ZiLOG
Model	Z8
Category	Desktop
Language	English