Z86L7808PSC View Datasheet(PDF) - Zilog
Part Name
Description
MFG CO.
'Z86L7808PSC' PDF : 59 Pages View PDF
Zilog
Z86L78
IR/Low-Voltage Microcontroller
RAM. The Z86L78 has 512-bytes of RAM and 256 bytes The upper nibble of the register pointer (Figure 18) selects
make-up the Register file. The remaining 256 bytes make which group of 16 bytes in the register file, out of the full
up the Extended Data RAM.
1 256 bytes, will be accessed. The lower nibble selects the
expanded register file bank and, in the case of the Z86L78,
Extended Data RAM. The Extended Data RAM occupies Banks F and D are implemented. A 0H in the lower nibble
the address range. FF00H-FFFFH (256 bytes). Accessing will allow the normal register file to be addressed, but any
the Extended Data RAM is accomplished by using LDE in- other value from 1H to FH will exchange the lower 16 reg-
struction only.
isters in favor of an expanded register group of 16 regis-
ters.
Note: The Extended Data RAM cannot be used as Stack
or instructions/code memory.
For example:
Expanded Register File (ERF). The standard Z8 register
file has been expanded to allow for additional system con-
trol registers, and for mapping of additional peripheral de-
vices along with I/O ports into the register address area.
The Z8 register address space R0 through R15 has been
implemented as 16 groups of 16 registers per group.
These register groups are known as the Expanded Regis-
ter File (ERF). Bits 7-4 of register RP select the working
register group. Bits 3-0 of register RP select the expanded
register group (Figure 16).
R253 RP
D7 D6 D5 D4 D3 D2 D1 D0
Z86L78: (See Figure 17)
R253 RP = 00H
R0 = Port 0
R1 = Port 1
R2 = Port 2
R3 = Port 3
But if:
R253 RP = 0DH
R0 = CTRL0
R1 = CTRL1
R2 = CTRL2
R3 = Reserved
The counter/timers are mapped into ERF group D. Access
is easily done using the following example:
Default Setting After Reset = 0000 0000
Expanded Register
File Pointer
Working Register
Pointer
LD RP, #0DH Select ERF D for access and register Bank
0 as the working register group
LD R0,#xx access CTRL0
Figure 15. Register Pointer Register
LD1, #xx access CTRL1
LDRP, #7DH Select expanded register group (ERF) group
D for access and register Bank 7 as the working reg-
ister bank
LDR1, 2 CTRL2 → register 71H
DS97LVO0701
2-21
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