3 CPU AND DEBUGGER
S1C17M20/M21/M22/M23/M24/M25
Seiko Epson Corporation
3-1
TECHNICAL MANUAL (Rev. 1.0)
3 CPU and Debugger
3.1 Overview
This IC incorporates the Seiko Epson original 16-bit CPU core (S1C17) with a debugger. The main features of the
CPU core are listed below.
• Seiko Epson original 16-bit RISC processor
- 24-bit general-purpose registers: 8
- 24-bit special registers:
2
- 8-bit special register:
1
- Up to 16M bytes of memory space (24-bit address)
- Harvard architecture using separated instruction bus and data bus
• Compact and fast instruction set optimized for development in C language
- Code length:
16-bit fixed length
- Number of instructions:
111 basic instructions (184 including variations)
- Execution cycle:
Main instructions are executed in one cycle.
- Extended immediate instructions: Immediate data can be extended up to 24 bits.
• Supports reset, NMI, address misaligned, debug, and external interrupts.
- Reads a vector from the vector table and branches to the interrupt handler routine directly.
- Can generate software interrupts with a vector number specified (all vector numbers specifiable).
• HALT mode (halt instruction) and SLEEP mode (slp instruction) are provided as the standby function.
• Incorporates a debugger with three-wire communication interface to assist in software development.
Interrupt
controller
Flash
memory
Interrupt request
Interrupt level
Vector number
Instruction bus
RAM
RAM bus
Debugger
Bus controller
Internal bus
General-purpose registers
CPU core (S1C17)
Bit 23
Bit 0
R7
Processor status register
IL[2:0] (Bits [7:5]): Interrupt Level
IE
(Bit 4):
Interrupt Enable
C
(Bit 3):
Carry
V
(Bit 2):
Overflow
Z
(Bit 1):
Zero
N
(Bit 0):
Negative
NMI
SYSCLK
DCLK
DSIO
DST2
Bit 7
Bit 0
PSR
Special registers
Program counter
Bit 23
Bit 0
PC
Stack pointer
Bit 23
Bit 0
SP
R6
R5
R4
R3
R2
R1
R0
Figure 3.1.1 S1C17 Configuration