Z86U18 Datasheet, PDF (13/30 Pages) Zilog, Inc. – USB Device Controller with CMOS Z86K15 MCU

Zilog
FUNCTIONAL DESCRIPTION
Program Memory. The 16-bit program counter addresses
4 KB of program memory space at internal locations (Fig-
ure 12).
The first 12 bytes of program memory are reserved for the
interrupt vectors. These locations have five 16-bit vectors
that correspond to the six available interrupts.
Byte 12 to byte 4095 consists of on-chip, mask pro-
grammed ROM. Addresses 4096 and greater are re-
served. The 4 KB program memory is mask programma-
ble.
Z86U18
USB Device Controller with CMOS Z86K15 MCU
R253 RP
1
D7 D6 D5 D4 D3 D2 D1 D0
Bank Pointer
Default setting after RESET = 00000000
Working Register
Group
Figure 13. Register Pointer Register
65535
4096
4095
Location of
First Byte of
Instruction
Executed 12
After RESET
11
10
9
8
7
Interrupt
Vector ₆
(Lower Byte)
5
4
Interrupt
Vector ₃
(Upper Byte)
2
1
0
Reserved
On-Chip
ROM
Reserved
Reserved
(T0)
(USB)
P31
(IRQ2)
P33
(IRQ1)
P32
(IRQ0)
Register File. The register file consists of four I/O port reg-
isters, 188 general-purpose registers and 11 control and
status registers (R3-R0, R4-191, and R255-R240, respec-
tively). The instructions can access registers directly or in-
directly through an 8-bit address field. This allows short, 4-
bit register addressing using the Register Pointer (Figure
13). In the 4-bit mode, the register file is divided into12
working-register groups, each occupying 16 continuous lo-
cations. The Register Pointer addresses the starting loca-
tion of the active working register group.
Note: To use the Bank Pointer: The instruction SRP 01
must be used to access the USB registers in the Expanded
Register File Space. These 8 registers (as defined on pp.
21-24) are available along with those registers from 10h to
BFh. Setting SRP 0 will allow access to the register loca-
tions 0 to BFh, including the I/O port registers at 0-3.
Figure 12. Program Memory Map
DS97KEY0102
PRELIMINARY
13