em78p257 ELAN Microelectronics Corp, em78p257 Datasheet - Page 10

• Manufacturer Part Number: em78p257
• Description: 8-bit Microcontroller
• Manufacturer: ELAN Microelectronics Corp

4. FUNCTION DESCRIPTION
4.1 Operational Registers
R0 is not a physically implemented register. Its major function is to be an indirect addressing pointer. Any instruction using
R0 as a pointer actually accesses data pointed by the RAM Select Register (R4).
This specification is subject to change without prior notice.
1. R0 (Indirect Addressing Register)
2. R1 (Time Clock /Counter)/TCC
3. R2 (Program Counter) & Stack/PC
• Increased by an external signal edge which is defined by the TE bit (CONT-4) through the TCC pin,
• Writable and readable as any other registers.
• The prescaler (RC) is assigned to TCC.
• The contents of the prescaler counter is cleared only when a value is written to TCC register.
TCC4/CIN1+/P50
or by the instruction cycle clock.
OSCI/CIN1-/P55
TCC/CIN2-/P54
TCC3/CO1/P51
CIN2+/P53
TCC5/P56
TCC6/P57
OSCI
CO2/P52
Oscillator Timing
Built-in
OSCO /RESET
Control
OSC
PORT5
I/O
RAM
R4
IOC5
R5
Prescaler
Fig. 3 Functional block diagram
WDT timer
R1(TCC)
DATA & CONTROL BUS
Comparator
TCC
Interrupt
controller
/INT
10
COUNTER
Instruction
Instruction
decoder
Register
ROM
IOC6/7
R6/7
PORT6/7
I/O
R2
R3
STACK 0
STACK 1
STACK 2
STACK 3
STACK 4
STACK 5
STACK 7
STACK 6
ALU
ACC
P60/INT
P61/CIN3-/TCC1
P62/CIN3+
P63/CO3
P64/CO4
P65/CIN4+
P66/CIN4-/TCC2
P67/IR OUT
P70/OSCO
P71//RESET
EM78P257
07.27.2004 (V1.4)
OTP ROM