ST92124V1Q-Auto STMicroelectronics, ST92124V1Q-Auto Datasheet - Page 94

• Manufacturer Part Number: ST92124V1Q-Auto
• Description: 8-bit MCU for automotive
• Manufacturer: STMicroelectronics

Specifications of ST92124V1Q-Auto

• Internal Memory: Single Voltage FLASH up to 256 Kbytes, RAM up to 8Kbytes, 1K byte E3 TM (Emulated EEPROM)
• Minimum Instruction Time: 83 ns (24 MHz int. clock)

ST92124xxx-Auto/150xxxxx-Auto/250xxxx-Auto
5.3 INTERRUPT PRIORITY LEVELS
The ST9 supports a fully programmable interrupt
priority structure. Nine priority levels are available
to define the channel priority relationships:
– The on-chip peripheral channels and the eight
– The 9th level (Top Level Priority) is reserved for
5.4 PRIORITY LEVEL ARBITRATION
The 3 bits of CPL (Current Priority Level) in the
Central Interrupt Control Register contain the pri-
ority of the currently running program (CPU priori-
ty). CPL is set to 7 (lowest priority) upon reset and
can be modified during program execution either
by software or automatically by hardware accord-
ing to the selected Arbitration Mode.
During every instruction, an arbitration phase
takes place, during which, for every channel capa-
ble of generating an Interrupt, each priority level is
compared to all the other requests (interrupts or
DMA).
If the highest priority request is an interrupt, its
PRL value must be strictly lower (that is, higher pri-
ority) than the CPL value stored in the CICR regis-
ter (R230) in order to be acknowledged. The Top
Level Interrupt overrides every other priority.
5.4.1 Priority Level 7 (Lowest)
Interrupt requests at PRL level 7 cannot be ac-
knowledged, as this PRL value (the lowest possi-
ble priority) cannot be strictly lower than the CPL
value. This can be of use in a fully polled interrupt
environment.
5.4.2 Maximum Depth of Nesting
No more than 8 routines can be nested. If an inter-
rupt routine at level N is being serviced, no other
Interrupts located at level N can interrupt it. This
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external interrupt sources can be programmed
within eight priority levels. Each channel has a 3-
bit field, PRL (Priority Level), that defines its pri-
ority level in the range from 0 (highest priority) to
7 (lowest priority).
the Timer/Watchdog or the External Pseudo
Non-Maskable Interrupt. An Interrupt service
routine at this level cannot be interrupted in any
arbitration mode. Its mask can be both maskable
(TLI) or non-maskable (TLNM).
guarantees a maximum number of 8 nested levels
including the Top Level Interrupt request.
5.4.3 Simultaneous Interrupts
If two or more requests occur at the same time and
at the same priority level, an on-chip daisy chain,
specific to every ST9 version, selects the channel
with the highest position in the chain, as shown in
Table 18
Table 18. Daisy Chain Priority
* available on some devices only
5.4.4 Dynamic Priority Level Modification
The main program and routines can be specifically
prioritized. Since the CPL is represented by 3 bits
in a read/write register, it is possible to dynamically
modify the current priority value during program
execution. This means that a critical section can
have a higher priority with respect to other inter-
rupt requests. Furthermore it is possible to priori-
tize even the Main Program execution by modify-
ing the CPL during its execution. See
Highest Position
Lowest Position
INTA0 / Watchdog Timer
INTA1 / Standard Timer
INTB0 / Extended Function Timer 0 *
INTB1 / Extended Function Timer 1 *
INTC0 / E
INTC1 / SPI
INTD0 / RCCU
INTD1 / WKUP MGT
Multifunction Timer 0
INTE0/CAN0_RX0
INTE1/CAN0_RX1
INTF0/CAN0_TX
INTF1/CAN0_SCE
INTG0/CAN1_RX0 *
INTG1/CAN1_RX1 *
INTH0/CAN1_TX *
INTH1/CAN1_SCE *
INTI0/SCI-A *
JBLPD *
I
I
A/D Converter
Multifunction Timer 1
SCI-M
2
2
C bus Interface 0
C bus Interface 1 *
3 TM
/Flash
Figure
45.