ST92196A STMicroelectronics, ST92196A Datasheet - Page 237

• Manufacturer Part Number: ST92196A
• Description: 8/16-bit Mcu For Tv Applications With Up To 96k Rom, On-screen-display And 1 Or 2 Data Slicers
• Manufacturer: STMicroelectronics

ST92E196A/B & ST92T196A/B GENERAL DESCRIPTION
1GENERAL DESCRIPTION
1.1 INTRODUCTION
The ST92E196A/B and ST92T196A/B microcon-
trollers are the EPROM/OTP versions of the
ST92196A ROM devices and are suitable for prod-
uct prototyping and low volume production. Their
performance derives from the use of a flexible
256-register programming model for ultra-fast con-
text switching and real-time event response. The
intelligent on-chip peripherals offload the ST9 core
from I/O and data management processing tasks
allowing critical application tasks to get the maxi-
mum use of core resources. The ST92E196A/B
and ST92T196A/B devices support low power
consumption and low voltage operation for power-
efficient and low-cost embedded systems.
1.1.1 Core Architecture
The nucleus of the ST92196A/B is the enhanced
ST9 Core that includes the Central Processing
Unit (CPU), the register file, the interrupt and DMA
controller.
Three independent buses are controlled by the
Core: a 16-bit memory bus, an 8-bit register ad-
dressing bus and a 6-bit interrupt/DMA bus which
connects the interrupt and DMA controllers in the
on-chip peripherals with the core.
This multiple bus architecture makes the ST9 fam-
ily devices highly efficient for accessing on and
off-chip memory and fast exchange of data with
the on-chip peripherals.
The general-purpose registers can be used as ac-
cumulators, index registers, or address pointers.
Adjacent register pairs make up 16-bit registers for
addressing or 16-bit processing. Although the ST9
has an 8-bit ALU, the chip handles 16-bit opera-
tions, including arithmetic, loads/stores, and mem-
ory/register and memory/memory exchanges.
Many opcodes specify byte or word operations,
the hardware automatically handles 16-bit opera-
tions and accesses.
For interrupts or subroutine calls, the CPU uses a
system stack in conjunction with the stack pointer
(SP). A separate user stack has its own SP. The
separate stacks, without size limitations, can be in
on-chip RAM (or in Register File) or off-chip mem-
ory.
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1.1.2 Instruction Set
The ST9 instruction set consists of 94 instruction
types, including instructions for bit handling, byte
(8-bit) and word (16-bit) data, as well as BCD and
Boolean formats. Instructions have been added to
facilitate large program and data handling through
the MMU, as well as to improve the performance
and code density of C Function calls. 14 address-
ing modes are available, including powerful indi-
rect addressing capabilities.
The ST9’s bit-manipulation instructions are set,
clear, complement, test and set, load, and various
logic instructions (AND, OR, and XOR). Math func-
tions include add, subtract, increment, decrement,
decimal adjust, multiply, and divide.
1.1.3 Operating Modes
To optimize performance versus the power con-
sumption of the device, ST9 devices now support
a range of operating modes that can be dynami-
cally selected depending on the performance and
functionality requirements of the application at a
given moment.
Run Mode. This is the full speed execution mode
with CPU and peripherals running at the maximum
clock speed delivered by the Phase Locked Loop
(PLL) of the Clock Control Unit (CCU).
Slow Mode. Power consumption can be signifi-
cantly reduced by running the CPU and the periph-
erals at reduced clock speed using the CPU Pres-
caler and CCU Clock Divider.
Wait For Interrupt Mode. The Wait For Interrupt
(WFI) instruction suspends program execution un-
til an interrupt request is acknowledged. During
WFI, the CPU clock is halted while the peripheral
and interrupt controller keep running at a frequen-
cy programmable via the CCU. In this mode, the
power consumption of the device can be reduced
by more than 95% (Low Power WFI).
Halt Mode. When executing the HALT instruction,
and if the Watchdog is not enabled, the CPU and
its peripherals stop operating and the status of the
machine remains frozen (the clock is also
stopped). A reset is necessary to exit from Halt
mode.