ST7260E1 STMicroelectronics, ST7260E1 Datasheet - Page 22

• Manufacturer Part Number: ST7260E1
• Description: LOW SPEED USB 8-BIT MCU FAMILY WITH UP TO 8K FLASH/ROM AND SERIAL COMMUNICATION INTERFACE (SCI)
• Manufacturer: STMicroelectronics

Specifications of ST7260E1

• 4 Or 8 Kbytes Program Memory: high density Flash (HDFlash), or FastROM with readout and write protection

Central processing unit (CPU)
6.3.1
6.3.2
6.3.3
6.3.4
22/139
Accumulator (A)
The Accumulator is an 8-bit general purpose register used to hold operands and the results
of the arithmetic and logic calculations and to manipulate data.
Index registers (X and Y)
In indexed addressing modes, these 8-bit registers are used to create effective addresses or
as temporary storage areas for data manipulation. (The Cross-Assembler generates a
precede instruction (PRE) to indicate that the following instruction refers to the Y register.)
The Y register is not affected by the interrupt automatic procedures (not pushed to and
popped from the stack).
Program counter (PC)
The program counter is a 16-bit register containing the address of the next instruction to be
executed by the CPU. It is made of two 8-bit registers PCL (Program Counter Low which is
the LSB) and PCH (Program Counter High which is the MSB).
Condition code register (CC)
The 8-bit Condition Code register contains the interrupt mask and four flags representative
of the result of the instruction just executed. This register can also be handled by the PUSH
and POP instructions. These bits can be individually tested and/or controlled by specific
instructions.
Table 8.
CC
BIt Name
4
7
1
H
Half carry
CC register description
This bit is set by hardware when a carry occurs between bits 3 and 4 of the ALU
during an ADD or ADC instructions. It is reset by hardware during the same
instructions.
0: No half carry has occurred.
1: A half carry has occurred.
This bit is tested using the JRH or JRNH instruction. The H bit is useful in BCD
arithmetic subroutines.
6
1
5
1
R/W
H
4
Function
R/W
3
I
R/W
N
2
Reset value: 111x1xxx
R/W
1
Z
ST7260xx
R/W
C
0