SDA5523 Micronas Semiconductor, SDA5523 Datasheet - Page 49

• Manufacturer Part Number: SDA5523
• Description: SDA55xx TVText Pro
• Manufacturer: Micronas Semiconductor

DATA SHEET
2.5.3. Memory Extension
The controller provides four additional address lines
A16, A17, A18 and A19. These additional address
lines are used to access program and data memory
space of up to 1MByte. The extended memory space
is split into 16 banks of 64 KByte each.
A16 is available as a dedicated pin, A17, A18 and A19
however work as alternate function to port pins P4.0,
P4.1 and P4.4 respectively. Refer to register CSCR1
(A19_P4_4, A18_P4_1,A17_P4_0).
The functionality for memory extension is provided by
a Memory management Unit (MMU) which includes
the four SFR registers MEX1, MEX2, MEX3 and
MEXSP.
2.5.3.1. Memory Extension Registers
The following registers are present in the Memory
management unit.
Table 2–27: Related registers
.
Micronas
Register Name
MEX1
MEX2
MEX3
MEXSP
See Section 3. on page 110 for detailed register description.
7
MM
MB19
Reserved
6
UB3
CB[19:16]
5
MB[18:16]
UB4
Sept. 10, 2004; 6251-556-3DS
4
MX19
These registers can be read and written through MOV
instructions like any other SFR register. Except for the
CB bits in MEX1 - which are read only - and can be
written only by the MMU. During normal operation user
must not write to the MEXSP register.
2.5.3.2. Reset Value
In order to insure proper 8051 functionality all the bits
in SFR MEX1, MEX2, MEX3 and MEXSP are initial-
ized to ‘0’
Bit Name
3
MXM
SP[6:0]
2
NB[19:16]
IB[19:16)
1
MX[18:16]
SDA 55xx
0
49