DS87C530 Maxim, DS87C530 Datasheet - Page 5

• Manufacturer Part Number: DS87C530
• Description: The DS87C530/DS83C530 EPROM/ROM microcontrollers with a real-time clock (RTC) are 8051-compatible microcontrollers based on the Dallas Semiconductor high-speed core
• Manufacturer: Maxim

PIN DESCRIPTION (continued)
PLCC
38
39
50
49
48
47
46
45
44
43
10
3
4
5
6
7
8
9
PIN
TQFP
31
32
43
42
41
40
39
38
37
36
48
49
50
51
52
1
2
3
P0.0 (AD0)
P0.1 (AD1)
P0.2 (AD2)
P0.3 (AD3)
P0.4 (AD4)
P0.5 (AD5)
P0.6 (AD6)
P0.7 (AD7)
NAME
PSEN
ALE
P1.0
P1.1
P1.2
P1.3
P1.4
P1.5
P1.6
P1.7
Program Store-Enable Output. This active-low signal is a chip enable for optional
external ROM memory. PSEN provides an active-low pulse and is driven high when
external ROM is not being accessed.
Address Latch-Enable Output. This pin latches the external address LSB from the
multiplexed address/data bus on Port 0. This signal is commonly connected to the
latch enable of an external 373 family transparent latch. ALE has a pulse width of
1.5 XTAL1 cycles and a period of four XTAL1 cycles. ALE is forced high when the
device is in a Reset condition. ALE can be disabled and forced high by writing
ALEOFF = 1 (PMR.2). ALE operates independently of ALEOFF during external
memory accesses.
Port 0 (AD0–AD7), I/O. Port 0 is an open-drain, 8-bit, bidirectional I/O port. As an
alternate function Port 0 can function as the multiplexed address/data bus to access
off-chip memory. During the time when ALE is high, the LSB of a memory address
is presented. When ALE falls to a logic 0, the port transitions to a bidirectional data
bus. This bus is used to read external ROM and read/ write external RAM memory
or peripherals. When used as a memory bus, the port provides active high drivers.
The reset condition of Port 0 is tri-state. Pullup resistors are required when using
Port 0 as an I/O port.
Port 1, I/O. Port 1 functions as both an 8-bit, bidirectional I/O port and an alternate
functional interface for Timer 2 I/O, new External Interrupts, and new Serial Port 1.
The reset condition of Port 1 is with all bits at a logic 1. In this state, a weak pullup
holds the port high. This condition also serves as an input mode, since any external
circuit that writes to the port will overcome the weak pullup. When software writes a
0 to any port pin, the device will activate a strong pulldown that remains on until
either a 1 is written or a reset occurs. Writing a 1 after the port has been at 0 will
cause a strong transition driver to turn on, followed by a weaker sustaining pullup.
Once the momentary strong driver turns off, the port again becomes the output high
(and input) state. The alternate modes of Port 1 are outlined as follows.
Port
P1.0
P1.1
P1.2
P1.3
P1.4
P1.5
P1.6
P1.7
DS87C530/DS83C530 EPROM/ROM Microcontrollers with Real-Time Clock
Alternate
T2
T2EX
RXD1
TXD1
INT2
INT3
INT4
INT5
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Function
External I/O for Timer/Counter 2
Timer/Counter 2 Capture/Reload Trigger
Serial Port 1 Input
Serial Port 1 Output
External Interrupt 2 (Positive Edge Detect)
External Interrupt 3 (Negative Edge Detect)
External Interrupt 4 (Positive Edge Detect)
External Interrupt 5 (Negative Edge Detect)
FUNCTION