P87C51FA-4N NXP Semiconductors, P87C51FA-4N Datasheet - Page 17

• Manufacturer Part Number: P87C51FA-4N
• Description: IC, 8BIT MCU, 80C51, 16MHZ, DIP-40
• Manufacturer: NXP Semiconductors

Specifications of P87C51FA-4N

• Controller Family/series: 80C51
• No. Of I/o's: 32
• Ram Memory Size: 256Byte
• Cpu Speed: 16MHz
• No. Of Timers: 4
• No. Of Pwm Channels: 5
• Core Size: 8 Bit
• Program Memory Size: 8KB
• Package: 40PDIP
• Device Core: 80C51
• Family Name: 87C
• Maximum Speed: 16 MHz
• Ram Size: 256 Byte
• Operating Supply Voltage: 3.3|5 V
• Data Bus Width: 8 Bit
• Program Memory Type: EPROM
• Number Of Programmable I/os: 32
• Interface Type: UART
• Operating Temperature: 0 to 70 °C
• Number Of Timers: 3
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

1. L = Level activated
2. T = Transition activated
Philips Semiconductors
Interrupt Priority Structure
The 8XC51 and 80C31 only have a 6-source four-level interrupt
structure. They are the IE, IP and IPH. (See Figures 10, 11, and 12.)
The IPH (Interrupt Priority High) register that makes the four-level
interrupt structure possible. The IPH is located at SFR address B7H.
The structure of the IPH register and a description of its bits is
shown in Figure 12.
The function of the IPH SFR is simple and when combined with the
IP SFR determines the priority of each interrupt. The priority of each
interrupt is determined as shown in the following table:
Table 7.
NOTES:
2000 Jan 20
80C51 8-bit microcontroller family
4K/128 OTP/ROM/ROMless, low voltage (2.7V–5.5V),
low power, high speed (33 MHz)
IPH.x
PRIORITY BITS
0
0
1
1
SOURCE
BIT
IE.7
IE.6
IE.5
IE.4
IE.3
IE.2
IE.1
IE.0
SP
X0
T0
X1
T1
T2
Interrupt Table
IE (0A8H)
IP.x
0
1
0
1
SYMBOL
EA
—
ET2
ES
ET1
EX1
ET0
EX0
Level 0 (lowest priority)
Level 1
Level 2
Level 3 (highest priority)
INTERRUPT PRIORITY LEVEL
INTERRUPT PRIORITY LEVEL
POLLING PRIORITY
Enable Bit = 1 enables the interrupt.
Enable Bit = 0 disables it.
FUNCTION
Global disable bit. If EA = 0, all interrupts are disabled. If EA = 1, each interrupt can be individually
enabled or disabled by setting or clearing its enable bit.
Not implemented. Reserved for future use.
Timer 2 interrupt enable bit.
Serial Port interrupt enable bit.
Timer 1 interrupt enable bit.
External interrupt 1 enable bit.
Timer 0 interrupt enable bit.
External interrupt 0 enable bit.
EA
7
1
2
3
4
5
6
—
6
ET2
5
Back
Figure 10. IE Registers
REQUEST BITS
ES
4
TF2, EXF2
RI, TI
TP0
TF1
IE0
IE1
17
ET1
3
An interrupt will be serviced as long as an interrupt of equal or
higher priority is not already being serviced. If an interrupt of equal
or higher level priority is being serviced, the new interrupt will wait
until it is finished before being serviced. If a lower priority level
interrupt is being serviced, it will be stopped and the new interrupt
serviced. When the new interrupt is finished, the lower priority level
interrupt that was stopped will be completed.
Next
EX1
2
HARDWARE CLEAR?
N (L)
ET0
N (L) Y (T)
1
1
Y
Y
N
N
Y (T)
EX0
80C51/87C51/80C31
0
2
VECTOR ADDRESS
Product specification
SU00571
0BH
1BH
2BH
03H
13H
23H