BS67F340 Datasheet, PDF (44/281 Pages) Holtek Semiconductor Inc – Enhanced Touch A/D Flash MCU with LCD Driver

BS67F340/BS67F350/BS67F360/BS67F370
Enhanced Touch A/D Flash MCU with LCD Driver
System Architecture
A key factor in the high-performance features of the Holtek range of microcontrollers is attributed
to their internal system architecture. The range of devices take advantage of the usual features found
within RISC microcontrollers providing increased speed of operation and enhanced performance.
The pipelining scheme is implemented in such a way that instruction fetching and instruction
execution are overlapped, hence instructions are effectively executed in one or two cycles for
most of the standard or extended instructions respectively, with the exception of branch or call
instructions which need one more cycle. An 8-bit wide ALU is used in practically all instruction set
operations, which carries out arithmetic operations, logic operations, rotation, increment, decrement,
branch decisions, etc. The internal data path is simplified by moving data through the Accumulator
and the ALU. Certain internal registers are implemented in the Data Memory and can be directly
or indirectly addressed. The simple addressing methods of these registers along with additional
architectural features ensure that a minimum of external components is required to provide a
functional I/O and A/D control system with maximum reliability and flexibility. This makes these
devices suitable for low-cost, high-volume production for controller applications.
Clocking and Pipelining
The main system clock, derived from either a HXT, LXT, HIRC or LIRC oscillator is subdivided
into four internally generated non-overlapping clocks, T1~T4. The Program Counter is incremented
at the beginning of the T1 clock during which time a new instruction is fetched. The remaining
T2~T4 clocks carry out the decoding and execution functions. In this way, one T1~T4 clock
cycle forms one instruction cycle. Although the fetching and execution of instructions takes place
in consecutive instruction cycles, the pipelining structure of the microcontroller ensures that
instructions are effectively executed in one instruction cycle. The exception to this are instructions
where the contents of the Program Counter are changed, such as subroutine calls or jumps, in which
case the instruction will take one more instruction cycle to execute.
For instructions involving branches, such as jump or call instructions, two machine cycles are
required to complete instruction execution. An extra cycle is required as the program takes one
cycle to first obtain the actual jump or call address and then another cycle to actually execute the
branch. The requirement for this extra cycle should be taken into account by programmers in timing
sensitive applications.
O s c illa to r C lo c k
( S y s te m C lo c k )
P h a s e C lo c k T 1
P h a s e C lo c k T 2
P h a s e C lo c k T 3
P h a s e C lo c k T 4
P ro g ra m C o u n te r
PC
PC +1
PC +2
P ip e lin in g
F e tc h In s t. (P C )
E x e c u te In s t. (P C -1 )
F e tc h In s t. (P C + 1 )
E x e c u te In s t. (P C )
System Clocking and Pipelining
F e tc h In s t. (P C + 2 )
E x e c u te In s t. (P C + 1 )
Rev. 1.40
44
December 15, 2016