SC61860 is an 8-bit microprocessor developed by Hitachi with ESR-H architecture. The processors of this architecture were widely used in the 80s in portable microcomputers ( Sharp PC-12xx, 13xx and 14xx) and organizers (Sharp PA-6/7/8000, S1, T1, X1 / 2/3, etc.).
Content
Processor Registers
- Pointer Registers for External Memory
The processor has two 16-bit registers designed for addressing external memory: PC (software counter) and DP (general purpose).
- Pointer registers for internal RAM
This function is performed by three 7-bit registers (P, Q, R). Since the amount of internal RAM is 96 bytes, 7 bits of the register is enough.
- Arithmetic registers
- Two 16-bit registers X and Y, high and low parts are available through 8-bit registers XL, XH, YL and YH
- Two 8-bit batteries, A and B
- Two 8-bit index registers, I and J
- Four 8-bit general purpose registers: K, L, M, and N
Memory Structure
- Internal RAM
The amount of internal RAM is 96 bytes. Some registers (including the battery) are mapped to this space. Also there are the system stack and part of the input / output ports. Internal RAM is more convenient to use and has a higher access speed compared to external. Data bus width 8 bits. Higher bit capacity data is stored in direct order (little-endian).
- External memory
An external address space of 64 KB has an address range of 0x0000-0xFFFF. The initial portion of addresses in the range 0x0000-0x1FFF (size 8 kbytes) has the name "internal ROM", which is physically located in the processor and is addressed only through the PC register. Program code and data are stored in external memory. The data bus is 8 bits wide. Bigger data is stored in reverse order (big-endian).
List of registers and their mapping to internal RAM
| Register | RAM address | Appointment |
|---|---|---|
| P | - | Register-pointer for internal RAM (7 bits) |
| Q | - | Register-pointer for internal RAM (7 bits) |
| R | - | Register-pointer for internal RAM (7 bits), stack pointer |
| PC | - | Register pointer for external memory (software counter, 16 bit) |
| DP | - | Pointer register for external memory (16 bits) |
| D | Internal index register | |
| I | 0x00 | Counter |
| J | 0x01 | Counter |
| A | 0x02 | Battery (8 bit) |
| B | 0x03 | Additional battery (8 bit) |
| K, L, M, N | 0x08..0x0B | General Purpose Registers (8 bits) |
| 0x0C..0x5B | System stack | |
| XL | 0x04 | Register 16-bit X = XL + 256 × XH |
| Xh | 0x05 | |
| Yl | 0x06 | Register 16-bit Y = YL + 256 × YH |
| Yh | 0x07 | |
| IA | 0x5C | I / O Port A |
| IB | 0x5D | I / O Port B |
| Fo | 0x5E | I / O Port F |
| OUTC | 0x5F | Control port |
Links
- SC61860 (ESR-H or old-SC) basics . Date of treatment August 27, 2011. Archived February 15, 2008.
- Machine Language Quick Manual for the Sharp PC-1360 (inaccessible link) . Date of treatment August 27, 2011. Archived January 4, 2009.