
ST72334J/N, ST72314J/N, ST72124J
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18 DEVICE CONFIGURATION AND ORDERING INFORMATION
Each device is available for production in user pro-
grammable versions (FLASH) as well as in factory
coded versions (ROM). E2PROM data memory
and FLASH devices are shipped to customers with
a default content (FFh), while ROM factory coded
parts contain the code supplied by the customer.
This implies that FLASH devices have to be con-
figured by the customer using the Option Bytes
while the ROM devices are factory-configured.
18.1 OPTION BYTES
The two option bytes allow the hardware configu-
ration of the microcontroller to be selected.
The option bytes have no address in the memory
map and can be accessed only in programming
mode (for example using a standard ST7 program-
ming tool). The default content of the FLASH is
fixed to FFh.
In masked ROM devices, the option bytes are
fixed in hardware by the ROM code (see option
list).
USER OPTION BYTE 0
Bit 7:2 = Reserved, must always be 1.
Bit 1 = 56/42
Package Configuration.
This option bit allows to configured the device ac-
cording to the package.
0: 42 or 44 pin packages
1: 56 or 64 pin packages
Bit 0 = FMP
Full memory protection.
This option bit enables or disables external access
to the internal program memory (read-out protec-
tion). Clearing this bit causes the erasing (by over-
writing with the currently latched values) of the
whole memory (not including the option bytes).
0: Program memory not read-out protected
1: Program memory read-out protected
Note: The data E2PROM is not protected by this
bit in flash devices. In ROM devices, a protection
can be selected in the Option List (see
page 146).USER OPTION BYTE 1
Bit 7 = CSS
Clock Security System disable
This option bit enables or disables the CSS fea-
tures.
0: CSS enabled
1: CSS disabled
Bit 6:4 = OSC[2:0]
Oscillator selection
These three option bits can be used to select the
Bit 3:2 = LVD[1:0]
Low voltage detection selection
These option bits enable the LVD block with a se-
Bit 1 = WDG HALT
Watchdog Reset on HALTt
mode
This option bit determines if a RESET is generated
when entering HALT mode while the Watchdog is
active.
0: No Reset generation when entering Halt mode
1: Reset generation when entering Halt mode
Bit 0 = WDG SW
Hardware or software watchdog
This option bit selects the watchdog type.
0: Hardware (watchdog always enabled)
1: Software (watchdog to be enabled by software)
Table 24. Main Oscillator Configuration
Table 25. LVD Threshold Configuration
Selected Oscillator
OSC2 OSC1 OSC0
External Clock (Stand-by)
11
1
~4 MHz Internal RC
11
0
1~14 MHz External RC
10
X
Low Power Resonator (LP)
01
1
Medium Power Resonator (MP)
01
0
Medium Speed Resonator (MS)
00
1
High Speed Resonator (HS)
00
0
Configuration
LVD1 LVD0
LVD Off
11
Highest Voltage Threshold (
4.50V)
10
Medium Voltage Threshold (
4.05V)
01
Lowest Voltage Threshold (
3.45V)
00
USER OPTION BYTE 0
70
USER OPTION BYTE 1
70
Reserved
56/42 FMP
CSS
OSC
2
OSC
1
OSC
0
LVD1 LVD0
WDG
HALT
WDG
SW
Default
Value
111111
X
0
1
1101
111