ISSI IS80C51-40WI, IS80C51-40PQI, IS80C51-40PQ, IS80C51-40PLI, IS80C51-40PL Datasheet
...
IS80C51
IS80C51
IS80C31
IS80C31
ISSI
ISSI
®
®
CMOS SINGLE CHIP
8-BIT MICROCONTROLLER
FEATURES
• 80C51 based architecture
• 4K x 8 ROM (IS80C51 only)
• 128 x 8 RAM
• Two 16-bit Timer/Counters
• Full duplex serial channel
• Boolean processor
• Four 8-bit I/O ports, 32 I/O lines
• Memory addressing capability
– 64K ROM and 64K RAM
• Power save modes:
– Idle and power-down
• Six interrupt sources
• Most instructions execute in 0.3 µs
• CMOS and TTL compatible
• Maximum speed: 40 MHz @ Vcc = 5V
• Industrial temperature available
• Packages available:
– 40-pin DIP
– 44-pin PLCC
– 44-pin PQFP
NOVEMBER 1998
GENERAL DESCRIPTION
The ISSI IS80C51 and IS80C31 are high-performance
microcontrollers fabricated using high-density CMOS
technology. The CMOS IS80C51/31 is functionally
compatible with the industry standard 80C51
microcontrollers.
The IS80C51/31 is designed with 4K x 8 ROM (IS80C51
only); 128 x 8 RAM; 32 programmable I/O lines; a serial
I/O port for either multiprocessor communications, I/O
expansion or full duplex UART; two 16-bit timer/counters;
a six-source, two-priority-level, nested interrupt structure;
and an on-chip oscillator and clock circuit. The
IS80C51/31 can be expanded using standard TTL
compatible memory.
40
39
38
37
36
35
34
33
32
31
30
29
28
27
26
25
24
23
22
21
VCC
P0.0/AD0
P0.1/AD1
P0.2/AD2
P0.3/AD3
P0.4/AD4
P0.5/AD5
P0.6/AD6
P0.7/AD7
EA/VPP
ALE/PROG
PSEN
P2.7/A15
P2.6/A14
P2.5/A13
P2.4/A12
P2.3/A11
P2.2/A10
P2.1/A9
P2.0/A8
P1.0
P1.1
P1.2
P1.3
P1.4
P1.5
P1.6
P1.7
RST
RxD/P3.0
TxD/P3.1
INT0/P3.2
INT1/P3.3
T0/P3.4
T1/P3.5
WR/P3.6
RD/P3.7
XTAL2
XTAL1
GND
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
Figure 1. IS80C51/31 Pin Configuration: 40-pin PDIP
ISSI reserves the right to make changes to its products at any time without notice in order to improve design and supply the best possible product. We assume no responsibility for any errors which
may appear in this publication. © Copyright 1998, Integrated Silicon Solution, Inc.
Integrated Silicon Solution, Inc. — 1-800-379-4774
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11/19/98
1
IS80C51
IS80C31
INDEX
P1.4
P1.3
P1.2
P1.1
P1.0NCVCC
P0.0/AD0
P0.1/AD1
P0.2/AD2
P0.3/AD3
®
ISSI
P1.5
P1.6
P1.7
RST
RxD/P3.0
NC
TxD/P3.1
INT0/P3.2
INT1/P3.3
T0/P3.4
T1/P3.5
4365 2144
7
8
9
10
11
12
13
14
15
16
17
18 19 20 21 22 23 24
XTAL2
RD/P3.7
WR/P3.6
TOP VIEW
GND
XTAL1
NC
43 42 41 40
25 26 27 28
A8/P2.0
A9/P2.1
A10/P2.2
39
38
37
36
35
34
33
32
31
30
29
A11/P2.3
A12/P2.4
P0.4/AD4
P0.5/AD5
P0.6/AD6
P0.7/AD7
EA/VPP
NC
ALE/PROG
PSEN
P2.7/A15
P2.6/A14
P2.5/A13
Figure 2. IS80C51/31 Pin Configuration: 44-pin PLCC
2
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IS80C51
IS80C31
P1.4
P1.3
P1.2
P1.1
P1.0NCVCC
P0.0/AD0
P0.1/AD1
P0.2/AD2
P0.3/AD3
®
ISSI
P1.5
P1.6
P1.7
RST
RxD/P3.0
NC
TxD/P3.1
INT0/P3.2
INT1/P3.3
T0/P3.4
T1/P3.5
42 4144 43 40 39 38
1
2
3
4
5
6
7
8
9
10
11
12 13 14 15 16 17 18
GND
XTAL1
RD/P3.7
WR/P3.6
XTAL2
NC
37 36 35 34
19 20 21 22
A8/P2.0
A9/P2.1
A10/P2.2
33
32
31
30
29
28
27
26
25
24
23
A11/P2.3
A12/P2.4
P0.4/AD4
P0.5/AD5
P0.6/AD6
P0.7/AD7
EA/VPP
NC
ALE/PROG
PSEN
P2.7/A15
P2.6/A14
P2.5/A13
Figure 3. IS80C51/31 Pin Configuration: 44-pin PQFP
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3
IS80C51
IS80C31
®
ISSI
VCC
RAM ADDR
REGISTER
B
REGISTER
P2.0-P2.7
P2
DRIVERS
ADDRESS
DECODER
& 128
BYTES RAM
STACK
POINT
PCON SCON TMOD TCON
TL1
TH0 TL0 TH1
SBUF IE IP
INTERRUPT BLOCK
SERIAL PORT BLOCK
TIMER BLOCK
P2
LATCH
ACC
TMP2
P0.0-P0.7
P0
DRIVERS
P0
LATCH
ALU
TMP1
ADDRESS
DECODER
&
4K ROM
PROGRAM
ADDRESS
REGISTER
PROGRAM
COUNTER
PC
INCREMENTER
PSEN
ALE
RST
EA
TIMING
AND
CONTROL
OSCILLATOR
REGISTER
INSTRUCTION
XTAL2XTAL1
PSW
P3
LATCH
P3
DRIVERS
P3.0-P3.7
P1
LATCH
P1
DRIVERS
P1.0-P1.7
Figure 4. IS80C51/31 Block Diagram
BUFFER
DPTR
4
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IS80C51
IS80C31
Table 1. Detailed Pin Description
Symbol PDIP PLCC PQFP I/O Name and Function
ALE 30 33 27 I/O Address Latch Enable: Output pulse for latching the low byte
of the address during an address to the external memory. In
normal operation, ALE is emitted at a constant rate of 1/6 the
oscillator frequency, and can be used for external timing or
clocking. Note that one ALE pulse is skipped during each
access to external data memory.
EA
P0.0-P0.7 39-32 43-36 37-30 I/O Port 0: Port 0 is an 8-bit open-drain, bidirectional I/O port. Port
31 35 29 I External Access enable: EA must be externally held low to
enable the device to fetch code from external program memory
locations 0000H to FFFFH. If EA is held high, the device
executes from internal program memory unless the program
counter contains an address greater than 0FFFH.
0 pins that have 1s written to them float and can be used as highimpedance inputs. Port 0 is also the multiplexed low-order
address and data bus during accesses to external program and
data memory. In this application, it uses strong internal pullups
when emitting 1s.
ISSI
®
P1.0-P1.7 1-8 2-9 40-44 I/O Port 1: Port 1 is an 8-bit bidirectional I/O port with internal
1-3 pullups. Port 1 pins that have 1s written to them are pulled high
by the internal pullups and can be used as inputs. As inputs,
Port 1 pins that are externally pulled low will source current
because of the internal pullups. (See DC Characteristics: IIL).
The Port 1 output buffers can sink/source four TTL inputs.
Port 1 also receives the low-order address byte during ROM
verification.
P2.0-P2.7 21-28 24-31 18-25 I/O Port 2: Port 2 is an 8-bit bidirectional I/O port with internal
pullups. Port 2 pins that have 1s written to them are pulled high
by the internal pullups and can be used as inputs. As inputs,
Port 2 pins that are externally pulled low will source current
because of the internal pullups. (See DC Characteristics: IIL).
Port 2 emits the high order address byte during fetches from
external program memory and during accesses to external data
memory that used 16-bit addresses (MOVX @ DPTR). In this
application, Port 2 uses strong internal pullups when emitting
1s. During accesses to external data memory that use 8-bit
addresses (MOVX @ Ri [i = 0, 1]), Port 2 emits the contents of
the P2 Special Function Register.
Port 2 also receives the high-order bits and some control
signals during ROM verification.
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IS80C51
IS80C31
®
ISSI
Table 1. Detailed Pin Description
Symbol PDIP PLCC PQFP I/O Name and Function
P3.0-P3.7 10-17 11, 13-19 5, 7-13 I/O Port 3: Port 3 is an 8-bit bidirectional I/O port with internal
10 11 5 I RxD (P3.0): Serial input port.
11 13 7 O TxD (P3.1): Serial output port.
12 14 8 I
13 15 9 I
14 16 10 I T0 (P3.4): Timer 0 external input.
15 17 11 I T1 (P3.5): Timer 1 external input.
16 18 12 O
17 19 13 O
PSEN
29 32 26 O Program Store Enable: The read strobe to external program
(continued)
pullups. Port 3 pins that have 1s written to them are pulled high
by the internal pullups and can be used as inputs. As inputs,
Port 3 pins that are externally pulled low will source current
because of the internal pullups. (See DC Characteristics: IIL).
Port 3 also serves the special features of the IS80LV51/31, as
listed below:
INT0INT0
INT0
(P3.2): External interrupt 0.
INT0INT0
INT1INT1
INT1
(P3.3): External interrupt 1.
INT1INT1
WRWR
WR
(P3.6): External data memory write strobe.
WRWR
RDRD
RD
(P3.7): External data memory read strobe.
RDRD
memory. When the device is executing code from the external
program memory,
except that two
access to external data memory.
fetches from internal program memory.
PSEN
is activated twice each machine cycle
PSEN
activations are skipped during each
PSEN
is not activated during
RST 9 10 4 I Reset: A high on this pin for two machine cycles while the
oscillator is running, resets the device. An internal MOS resistor
to GND permits a power-on reset using only an external
capacitor connected to Vcc.
XTAL 1 19 21 15 I Crystal 1: Input to the inverting oscillator amplifier and input
to the internal clock generator circuits.
XTAL 2 18 20 14 O Crystal 2: Output from the inverting oscillator amplifier.
GND 20 22 16 I Ground: 0V reference.
Vcc 40 44 38 I Power Supply: This is the power supply voltage for operation.
6
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IS80C51
IS80C31
OPERATING DESCRIPTION
®
ISSI
The detail description of the IS80C51/31 included in this
description are:
• Memory Map and Registers
• Timer/Counters
• Serial Interface
• Interrupt System
• Other Information
MEMORY MAP AND REGISTERS
Memory
The IS80C51/31 has separate address spaces for program
and data memory. The program and data memory can be
up to 64K bytes long. The lower 4K program memory can
reside on-chip. (IS80C51 only) Figure 5 shows a map of
the IS80C51/31 program and data memory.
The IS80C51/31 has 128 bytes of on-chip RAM, plus
numbers of special function registers. The lower 128 bytes
can be accessed either by direct addressing or by indirect
addressing. Figure 6 shows internal data memory
organization and SFR Memory Map.
The lower 128 bytes of RAM can be divided into three
segments as listed below and shown in Figure 7.
1.
Register Banks 0-3:
locations 00H through 1FH
(32 bytes). The device after reset defaults to register
bank 0. To use the other register banks, the user
must select them in software. Each register bank
contains eight 1-byte registers R0-R7. Reset initializes the stack point to location 07H, and is incremented
once to start from 08H, which is the first register of the
second register bank.
2.
Bit Addressable Area:
16 bytes have been assigned for this segment 20H-2FH. Each one of the
128 bits of this segment can be directly addressed (07FH). Each of the 16 bytes in this segment can also
be addressed as a byte.
3.
Scratch Pad Area:
30H-7FH are available to the
user as data RAM. However, if the data pointer has
been initialized to this area, enough bytes should be
left aside to prevent SP data destruction.
FFFFH:
64K
EA = 0
External
PSEN
Program Memory
(Read Only)
External External
0FFFH:
4K
EA = 1
Internal
0000
00
Data Memory
(Read/Write)
Internal
FFFFH
FFH
80H7FH
0000
Figure 5. IS80C51/31 Program and Data Memory Structure
RD WR
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IS80C51
IS80C31
SPECIAL FUNCTION REGISTERS
®
ISSI
The Special Function Registers (SFR's) are located in
upper 128 Bytes direct addressing area. The SFR Memory
Map in Figure 6 shows that.
Not all of the addresses are occupied. Unoccupied
addresses are not implemented on the chip. Read accesses
to these addresses in general return random data, and
write accesses have no effect.
User software should not write 1s to these unimplemented
locations, since they may be used in future microcontrollers
to invoke new features. In that case, the reset or inactive
values of the new bits will always be 0, and their active
values will be 1.
The functions of the SFRs are outlined in the following
sections, and detailed in Table 2.
FFH
Upper
128
Lower
128
80H
7FH
0
Not Available
in
IS80C51/31
Accessible
by Direct
and Indirect
Addressing
Accessible
by Direct
Addressing
Special
Function
Registers
80H
Ports,
Status and
Control Bits,
Timer,
Registers,
Stack Pointer,
Accumulator
(Etc.)
Accumulator (ACC)
ACC is the Accumulator register. The mnemonics for
Accumulator-specific instructions, however, refer to the
Accumulator simply as A.
B Register (B)
The B register is used during multiply and divide operations.
For other instructions it can be treated as another scratch
pad register.
Program Status Word (PSW). The PSW register contains
program status information.
F8
B
F0
E8
ACC
E0
D8
PSW
D0
C8
C0
IP
B8
P3
B0
IE
A8
P2
A0
98
90
88
80
Addressable
SCON
TCON
P1
P0
Bit
SBUF
TMODSPTL0
DPL
TL1
DPH
TH0 TH1
PCON
FF
F7
EF
E7
DF
D7
CF
C7
BF
B7
AF
A7
9F
97
8F
87
Figure 6. Internal Data Memory and SFR Memory Map
8 BYTES
78
70
68
60
58
50
48
40
38
30
28
0 ...
20
18
10
08
00
BANK3
BANK2
BANK 1
BANK 0
...7F
7F
77
6F
67
5F
SCRATCH
57
4F
47
3F
37
2F
ADDRESSABLE
27
SEGMENT
1F
17
REGISTER
0F
07
PAD
AREA
BIT
BANKS
Figure 7. Lower 128 Bytes of Internal RAM
8
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IS80C51
IS80C31
SPECIAL FUNCTION REGISTERS
(Continued)
®
ISSI
Stack Pointer (SP)
The Stack Pointer Register is eight bits wide. It is
incremented before data is stored during PUSH and CALL
executions. While the stack may reside anywhere in onchip RAM, the Stack Pointer is initialized to 07H after a
reset. This causes the stack to begin at location 08H.
Data Pointer (DPTR)
The Data Pointer consists of a high byte (DPH) and a low
byte (DPL). Its function is to hold a 16-bit address. It may
be manipulated as a 16-bit register or as two independent
8-bit registers.
Ports 0 To 3
P0, P1, P2, and P3 are the SFR latches of Ports 0, 1, 2, and
3, respectively.
Serial Data Buffer (SBUF)
The Serial Data Buffer is actually two separate registers,
a transmit buffer and a receive buffer register. When data
is moved to SBUF, it goes to the transmit buffer, where it
is held for serial transmission. (Moving a byte to SBUF
initiates the transmission.) When data is moved from
SBUF, it comes from the receive buffer.
Timer Registers
Register pairs (TH0, TL0) and (TH1, TL1) are the 16-bit
Counter registers for Timer/Counters 0 and 1, respectively.
Control Registers
Special Function Registers IP, IE, TMOD, TCON, SCON,
and PCON contain control and status bits for the interrupt
system, the Timer/Counters, and the serial port. They are
described in later sections of this chapter.
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IS80C51
IS80C31
Table 2. Special Function Register
Symbol Description Direct Address Bit Address, Symbol, or Alternative Port Function Reset Value
(1)
ACC
(1)
B
DPH Data pointer (DPTR) high 83H 00H
DPL Data pointer (DPTR) low 82H 00H
(1)
IE
(1)
IP
(1)
P0
(1)
P1
(1)
P2
(1)
P3
PCON Power control 87H SMOD — — — GF1 GF0 PD IDL 0XXX0000B
(1)
PSW
SBUF Serial data buffer 99H XXXXXXXXB
(1)
SCON
SP Stack pointer 81H 07H
(1)
TCON
TMOD Timer mode 89H GATE C/
TH0 Timer high 0 8CH 00H
TH1 Timer high 1 8DH 00H
TL0 Timer low 0 8AH 00H
TL1 Timer low 1 8BH 00H
Accumulator E0H E7 E6 E5 E4 E3 E2 E1 E0 00H
B register F0H F7 F6 F5 F4 F3 F2 F1 F0 00H
AF AE AD AC AB AA A9 A8
Interrupt enable A8H EA — — ES ET1 EX1 ET0 EX0 0XX00000B
BF BE BD BC BB BA B9 B8
Interrupt priority B8H — — — PS PT1 PX1 PT0 PX0 XXX00000B
87 86 85 84 83 82 81 80
Port 0 80H P0.7 P0.6 P0.5 P0.4 P0.3 P0.2 P0.1 P0.0 FFH
AD7 AD6 AD5 AD4 AD3 AD2 AD1 AD0
97 96 95 94 93 92 91 90
Port 1 90H P1.7 P1.6 P1.5 P1.4 P1.3 P1.2 P1.1 P1.0 FFH
A7 A6 A5 A4 A3 A2 A1 A0
Port 2 A0H P2.7 P2.6 P2.5 P2.4 P2.3 P2.2 P2.1 P2.0 FFH
AD15 AD14 AD13 AD12 AD11 AD10 AD9 AD8
B7 B6 B5 B4 B3 B2 B1 B0
Port 3 B0H P3.7 P3.6 P3.5 P3.4 P3.3 P3.2 P3.1 P3.0 FFH
RD WR
T1 T0
INT1 INT0
TXD RXD
D7 D6 D5 D4 D3 D2 D1 D0
Program status word D0H CY AC F0 RS1 RS0 OV — P 00H
9F 9E 9D 9C 9B 9A 99 98
Serial controller 98H SM0 SM1 SM2 REN TB8 RB8 TI RI 00H
8F 8E 8D 8C 8B 8A 89 88
Timer control 88H TF1 TR1 TF0 TR0 IE1 IT1 IE0 IT0 00H
T
M1 M0 GATE C/TM1 M0 00H
ISSI
®
Note:
1. Denotes bit addressable.
10
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IS80C51
IS80C31
The detail description of each bit is as follows:
®
ISSI
PSW:
Program Status Word. Bit Addressable.
76543210
CY AC F0 RS1 RS0 OV — P
Register Description:
CY PSW.7 Carry flag.
AC PSW.6 Auxiliary carry flag.
F0 PSW.5 Flag 0 available to the user for general
purpose.
RS1 PSW.4 Register bank selector bit 1.
RS0 PSW.3 Register bank selector bit 0.
(1)
(1)
OV PSW.2 Overflow flag.
— PSW.1 Usable as a general purpose flag
P PSW.0 Parity flag. Set/Clear by hardware each
instruction cycle to indicate an odd/even
number of “1” bits in the accumulator.
Note:
1. The value presented by RS0 and RS1 selects the corresponding register bank.
RS1 RS0 Register Bank Address
0 0 0 00H-07H
0 1 1 08H-0FH
1 0 2 10H-17H
1 1 3 18H-1FH
PCON:
Power Control Register. Not Bit Addressable.
76543210
SMOD — — — GF1 GF0 PD IDL
Register Description:
SMOD Double baud rate bit. If Timer 1 is used to generate
baud rate and SMOD=1, the baud rate is doubled
when the serial port is used in modes 1, 2, or 3.
— Not implemented, reserve for future use.
— Not implemented, reserve for future use.
— Not implemented, reserve for future use.
GF1 General purpose flag bit.
GF0 General purpose flag bit.
PD Power-down bit. Setting this bit activates power-
down mode.
IDL Idle mode bit. Setting this bit activates idle mode.
If 1s are written to PD and IDL at the same time,
PD takes precedence.
Note:
1. User software should not write 1s to reserved bits. These
bits may be used in future products to invoke new features.
(1)
(1)
(1)
IE:
Interrupt Enable Register. Bit Addressable.
76543210
EA — — ES ET1 EX1 ET0 EX0
Register Description:
EA IE.7 Disable all interrupts. If EA=0, no
interrupt will be acknowledged. If EA=1,
each interrupt source is individually
enabled or disabled by setting or
clearing its enable bit.
— IE.6 Not implemented, reserve for future
— IE.5 Not implemented, reserve for future
ES IE.4 Enable or disable the serial port
ET1 IE.3 Enable or disable the timer 1 overflow
EX1 IE.2 Enable or disable external interrupt 1.
ET0 IE.1 Enable or disable the timer 0 overflow
EX0 IE.0 Enable or disable external interrupt 0.
Note: To use any of the interrupts in the 80C51 Family, the
following three steps must be taken:
1. Set the EA (enable all) bit in the IE register to 1.
2. Set the coresponding individual interrupt enable bit in
the IE register to 1.
3. Begin the interrupt service routine at the corresponding
Vector Address of that interrupt (see below).
Interrupt Source Vector Address
IE0 0003H
TF0 000BH
IE1 0013H
TF1 001BH
RI & TI 0023H
4. In addition, for external interrupts, pins
(P3.2 and P3.3) must be set to 1, and depending on
whether the interrupt is to be level or transition activated, bits IT0 or IT1 in the TCON register may need to
be set to 0 or 1.
ITX = 0 level activated (X = 0, 1)
ITX = 1 transition activated
User software should not write 1s to reserved bits. These
5.
bits may be used in future products to invoke new
features.
(5)
use.
(5)
use.
interrupt.
interrupt.
interrupt.
INT0
and
INT1
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11
IS80C51
IS80C31
®
ISSI
IP:
Interrupt Priority Register. Bit Addressable.
76543210
— — — PS PT1 PX1 PT0 PX0
Register Description:
— IP.7 Not implemented, reserve for future use
— IP.6 Not implemented, reserve for future use
— IP.5 Not implemented, reserve for future use
PS IP.4 Defines Serial Port interrupt priority level
PT1 IP.3 Defines Timer 1 interrupt priority level
PX1 IP.2 Defines External Interrupt 1 priority level
PT0 IP.1 Defines Timer 0 interrupt priority level
PX0 IP.0 Defines External Interrupt 0 priority level
Notes:
1. In order to assign higher priority to an interrupt the
coresponding bit in the IP register must be set to 1. While
an interrupt service is in progress, it cannot be interrupted
by a lower or same level interrupt.
2. Priority within level is only to resolve simultaneous
requests of the same priority level. From high to low,
interrupt sources are listed below:
IE0
TF0
IE1
TF1
RI or TI
User software should not write 1s to reserved bits. These
3.
bits may be used in future products to invoke new features.
TCON:
Timer/Counter Control Register. Bit Addressable
76543210
TF1 TR1 TF0 TR0 IE1 IT1 IE0 IT0
Register Description:
(3)
TF1 TCON.7 Timer 1 overflow flag. Set by hardware
(3)
(3)
TR1 TCON.6 Timer 1 run control bit. Set/Cleared by
TF0 TCON.5 Timer 0 overflow flag. Set by hardware
TR0 TCON.4 Timer 0 run control bit. Set/Cleared by
IE1 TCON.3 External Interrupt 1 edge flag. Set by
IT1 TCON.2 Interrupt 1 type control bit. Set/Cleared
IE0 TCON.1 External Interrupt 0 edge flag. Set by
IT0 TCON.0 Interrupt 0 type control bit. Set/Cleared
when the Timer/Counter 1 overflows.
Cleared by hardware as processor
vectors to the interrupt service routine.
software to turn Timer/Counter 1 ON/
OFF.
when the Timer/Counter 0 overflows.
Cleared by hardware as processor
vectors to the interrupt service routine.
software to turn Timer/Counter 0 ON/
OFF.
hardware when the External Interrupt
edge is detected. Cleared by hardware
when interrupt is processed.
by software specify falling edge/low level
triggered External Interrupt.
hardware when the External Interrupt
edge is detected. Cleared by hardware
when interrupt is processed.
by software specify falling edge/low level
triggered External Interrupt.
12
Integrated Silicon Solution, Inc. — 1-800-379-4774
MC003-1D
11/19/98
IS80C51
IS80C31
®
ISSI
TMOD:
Timer/Counter Mode Control Register.
Not Bit Addressable.
Timer 1 Timer 0
GATE C/
TT
T
M1 M0 GATE C/
TT
GATE When TRx (in TCON) is set and GATE=1, TIMER/
COUNTERx will run only while INTx pin is high
(hardware control). When GATE=0, TIMER/
COUNTERx will run only while TRx=1 (software
control).
C/
T
Timer or Counter selector. Cleared for Timer
operation (input from internal system clock). Set for
Counter operation (input from Tx input pin).
M1 Mode selector bit.
M0 Mode selector bit.
Note 1:
M1 M0 Operating mode
0 0 Mode 0. (13-bit Timer)
0 1 Mode 1. (16-bit Timer/Counter)
1 0 Mode 2. (8-bit auto-load Timer/Counter)
1 1 Mode 3. (Splits Timer 0 into TL0 and TH0. TL0 is
an 8-bit Timer/Counter controller by the standard
Timer 0 control bits. TH0 is an 8-bit Timer and is
controlled by Timer 1 control bits.)
1 1 Mode 3. (Timer/Counter 1 stopped).
(1)
(1)
TT
T
M1 M0
TT
SCON:
Serial Port Control Register. Bit Addressable.
76543210
SM0 SM1 SM2 REN TB8 RB8 TI RI
Register Description:
SM0 SCON.7 Serial port mode specifier.
SM1 SCON.6 Serial port mode specifier.
SM2 SCON.5 Enable the multiprocessor com-
munication feature in mode 2 and 3. In
mode 2 or 3, if SM2 is set to 1 then RI will
not be activated if the received 9th data
bit (RB8) is 0. In mode 1, if SM2=1 then
RI will not be activated if valid stop bit
was not received. In mode 0, SM2 should
be 0.
REN SCON.4 Set/Cleared by software to Enable/
Disable reception.
TB8 SCON.3 The 9th bit that will be transmitted in
mode 2 and 3. Set/Cleared by software.
RB8 SCON.2 In modes 2 and 3, RB8 is the 9th data bit
that was received. In mode 1, if SM2=0,
RB8 is the stop bit that was received. In
mode 0, RB8 is not used.
TI SCON.1 Transmit interrupt flag. Set by hardware
at the end of the 8th bit time in mode 0,
or at the beginning of the stop bit in the
other modes. Must be cleared by
software.
RI SCON.0 Receive interrupt flag. Set by hardware
at the end of the 8th bit time in mode 0,
or halfway through the stop bit time in
the other modes (except see SM2). Must
be cleared by software.
Note:
(1)
(1)
Integrated Silicon Solution, Inc. — 1-800-379-4774
MC003-1D
11/19/98
SM0 SM1 MODE Description Baud rate
0 0 0 Shift register Fosc/12
0 1 1 8-bit UART Variable
1 0 2 9-bit UART Fosc/64 or Fosc/32
1 1 3 9-bit UART Variable
13
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