ST90158 - REGISTER AND MEMORY MAP
3 REGISTER AND MEMORY MAP
3.1 MEMORY CONFIGURATION
proximately 4000Å. It should be noted that sunlight
and some types of fluorescent lamps have wave-
lengths in the range 3000-4000Å. It is thus recom-
mended that the window of the ST90E158 packag-
es be covered by an opaque label to prevent unin-
tentional erasure problems when testing the appli-
cation in such an environment.
The Program memory space of the ST90135/158,
0/24/32/48/64/K bytes of directly addressable on-
chip memory, is fully available to the user.
The first 256 memory locations from address 0 to
FFh hold the Reset Vector, the Top-Level (Pseudo
Non-Maskable) interrupt, the Divide by Zero Trap
Routine vector and, optionally, the interrupt vector
table for use with the on-chip peripherals and the
external interrupt sources. Apart from this case no
other part of the Program memory has a predeter-
mined function except segment 21h which is re-
served for use by STMicroelectronics.
The recommended erasure procedure of the
EPROM is the exposure to short wave ultraviolet
light which have a wave-length 2537Å. The inte-
grated dose (i.e. U.V. intensity x exposure time) for
erasure should be a minimum of 15W-sec/cm2.
The erasure time with this dosage is approximate-
ly 30 minutes using an ultraviolet lamp with
12000mW/cm2 power rating. The ST90E158
should be placed within 2.5cm (1 inch) of the lamp
tubes during erasure.
3.2 EPROM PROGRAMMING
The 65536 bytes of EPROM memory of the
ST90E158 may be programmed by using the
EPROM Programming Boards (EPB) available
from STMicroelectronics or gang programmers
available from third party.
Table 5. First 6 Bytes of Program Space
0
1
2
3
4
5
Address high of Power on Reset routine
Address low of Power on Reset routine
Address high of Divide by zero trap Subroutine
Address low of Divide by zero trap Subroutine
Address high of Top Level Interrupt routine
Address low of Top Level Interrupt routine
EPROM Erasing
The EPROM of the windowed package of the
ST90E158 may be erased by exposure to Ultra-Vi-
olet light.
The erasure characteristic of the ST90E158 is
such that erasure begins when the memory is ex-
posed to light with a wave lengths shorter than ap-
37/199
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ETC [ ETC ]
