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LH5801 The LH5801 is an 8-bit microprocessor unit (MPU) in static CMOS technology produced by the Sharp Corporation [1] from around 1980 to mid/late 1980ies (exact dates to be researched). It was used in the Sharp PC-1500 pocket computer series[2]: 2–4 .

Overview

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Image of LH5801 microprocessor
LH5801 microprocessor (above) with LH5810 I/O chip below on a Sharp PC-1500 motherboard

The processor features an 8-bit wide data bus and 16 bit wide address bus, which allows 64KB of main memory. A 1-bit memory enable signal allows addressing of a further 64KB of external memory in direct access for a total of 128KB capacity[2]: 6 [3]. The processor has 3 16-bit exclusive registers P, S and W, an 8-bit accumulator, 8 bit status register and 3 general purpose 16-bit registers named U, X and Y, which can be addressed as separate 8-bit registers (for example UL and UH). The processor has a timer function, three types of interrupt (Maskable, non-maskable and timer), DMA and multiprocessor capabilities, memory access control functionality, an 8-bit input port with clock signal for external latch, memory backup function and LCD back plate control.[2]: 4 .

The processor works with a clock rate of 2.6MHz which yields an internal machine cycle of 1.3MHz for a minimum instruction execution time of 1.3µs for single cycle instructions[2]: 5 .

History

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The actual release date has to be researched, probably around 1980. Detailed information about the processor were made available to the public in English in 1983[4], before that most users were restricted to using BASIC as programming language in the pocket computers using this CPU.

Architecture

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The processor is an 8-bit CISC[Footnotes 1] CPU with a basic design similar to the Z80, but with additional I/O capabilities such as direct LCD display control circuitry and connectors, targeted for its main usage in Sharp' series of pocket computers.

Block diagram

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The block diagram was published in the PC-1500 Technical Reference Manual in 1983[3].

Internal Registers

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PH 8 PL 8 P Program counter
SH 8 SL 8 S Stack pointer
UH 8 UL 8 Ureg Data pointer or general purpose registers
XH 8 XL 8 Xreg
YH 8 YL 8 Yreg
A 8 A Accumulator
TM 9 TM Timer
1 PU General purpose flipflop
1 PV
1 DISP LCD on/off control

Status Flags

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MSB LSB
0 0 0 H V Z IE C
Flag Name Description
H Half Carry Set on overflow between lower and higher nibble, e.g. in BCD arithmetic.
V Overflow Set on overflow between bit 6 and 7 (change of sign)
Z Zero Set if operation result is zero
IE Interrupt enable
C Carry Set on carry from most significant bit 7, else reset. on substraction when 'borrowed'.

Connectors

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The processor as used in the Sharp PC-1500 is packaged in a 76 pin QFP variant (missing detailed measurements/documentation). The pins are numbered counterclockwise starting with the dot-marked corner.[2]

No. Name Description
1 RESET HIGH input for reset to initial state
2 -
3 BRQ Bus request. MPU sets BAK to high when current command execution is completed
4 BF1 BF flipflop output
5 Vcc
6 BF0 BF flipflop input
7 OPF Operation code fetch signal, high during fetch of instruction code byte
8 BAK Bus acknowledge appears in response with a high BRQ indicating that address bus, data bus, R/W, ME0 and ME1 are in high impedance
9 Vcc Voltage supply
10 -
11 VM LCD drive source
12 VDID
13 VA
14 VB
15 NMI Non maskable interrupt
16 MI Maskable interrupt
17 ¬HIN LCD backplate signal. Counter input htat generates H0~H7. Normally connected to HA
18 HA MPU divider output
19 DIS Flipflop: Set to high with the SDP instruction and set to low with the RDP instruction
20 H7 LCD backplate signal
21 H6
22 H5
23 H4
24 H3
25 H2
26 H1
27 H0
28 OD Output disable. When the OD signal is active the data bus is in the output mode.
29 ME0 Memory enable signals that the MPU uses for direct accessing to an external memory.
30 ME1
31 D0 Bidirectional data bus. D0: LSB, D7 MSB.
32 D1
33 D2
34 D3
35 D4
36 D5
37 D6
38 D7
39 AD0 16 bit address bus. AD0: LSB, AD15 MSB. Turns hign impedance by the BRQ signal.
40 AD1
41 AD2
42 AD3
43 AD4
44 AD5
45 AD6
46 AD7
47 GND
48 AD8
49 -
50 AD9
51 AD10
52 AD11
53 AD12
54 AD13
55 AD14
56 AD15
57 -
58 R/¬W Read/Write signal, Read = 1 and write = 0
59 Strobe output during execution of ATP instruction for externallatch of A register contents.
60 PV Flipflop: Set to high with the SPV instruction and set to low with the RPV instruction
61 PU Flipflop: Set to high with the SPU instruction and set to low with the RPU instruction
62 øOS Clock in same phase as basic internal clock, 1.3MHz frequenca when XL0 and XL1 are connected to a 2.6MHz quartz.
63 XL0 Crystal oscillator externel connection pins (XL0:in, XL1: out
64 XL1
65 WAIT Wait input that informs the MPU that addressed memory or I/O device is not ready. The MPU is in the wait state while this isgnal is on.
66 IN7 Input port. Input is taken into internal accumulator as 8 bit data.
67 IN6
68 IN5
69 IN4
70 IN3
71 IN2
72 IN1
73 IN0
74 -
75 -
76 -

Instruction Set

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Address modes

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The names are inserted here for clarification and are not taken from original documentation.

Syntax Name Description Example
i Immediate Use byte immediately following instruction ADI A, 20H
A Accumulator Use Accumulator as operand ADI A, 20H
i,j Immediate, 16bit 16bit immediate, first byte i=MSB, second j=LSB JMP A0H, 20H
RL Register low direct For register R, use content of lower byte. ADC YL
RH Register high direct For register R, use content of higher byte. ADC YH
(Rreg) Register indirect Use memory referenced by content of 16 bit register R ADC (Xreg)
# (Rreg) Register indirect ME 1 Same as register indirect, but with Memory Enabled pin 1 ADC # (Xreg)
(ab) Indirect Content from memory address ab (a MSB, b LSB) ADC (C000H)
# (ab) Indirect ME 1 Content from ME 1 address ab ADC # (C000H)

Addition, Substraction and logical operations

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Mnemonic Operation Description Status bits affected Address modes
ADC Add with Carry Operand will be added to acumulator with carry C H Z V
Mode Opcode

7 6 5 4 3 2 1 0

RL 0 0 r r 0 0 1 0
RH 1 0 r r 0 0 1 0
(Rreg) 0 0 r r 0 0 1 1
# (Rreg) FD

0 0 r r 0 0 1 1

(ab) 1 0 1 0 0 0 1 1
# (ab) FD

1 0 1 0 0 0 1 1

ADI Add immediately with carry Immediate value will be added to first operand with carry C H Z V
Mode Opcode

7 6 5 4 3 2 1 0

A,i 1 0 1 1 0 0 1 1
(R),i 0 1 r r 1 1 1 1
(ab),i 1 1 1 0 1 1 1 1
# (R),i FD

0 1 r r 1 1 1 1

# (ab),i FD

1 1 1 0 1 1 1 1

DCA Decimal Add Decimal addition betwen accumulator and operand. C H Z V
Mode Opcode

7 6 5 4 3 2 1 0

(Rreg) 1 0 r r 1 1 0 0
# (Rreg) FD

1 0 r r 1 1 0 0

References

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  1. ^ http://www.sharp.co.jp/
  2. ^ a b c d e Sharp Corporation, 1980?: "Sharp Service Manual for Model PC-1500 & Option" (Out of print)
  3. ^ a b "Sharp PC-1500 Technical Reference Manual". Sharp PC-1500 (TRS-80 PC-2) resource page. Sharp Corporation. Retrieved 2016-03-20.
  4. ^ "Neuerscheinung Sharp PC-1500 Machine Language Programming Manual Sharp Corporation". Sharp PC-1500 Taschencomputer Zeitung (in German) (1. Jahrgang Heft 1). Berlin: PC-1500 User Club. 1983-05-01.
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Footnotes


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