DS87C520-MCL+ Dallas Semiconductor, DS87C520-MCL+ Datasheet - Page 6

• Manufacturer Part Number: DS87C520-MCL+
• Description: Microcontroller, 8051 Comp., 4 8-Bit I/O Ports, 64K ROM/RAM, 33 MHz, 5 V, PDIP40
• Manufacturer: Dallas Semiconductor

Specifications of DS87C520-MCL+

• Eeprom Memory: 0 Bytes
• Input Output: 32
• Interface: UART
• Memory Type: EPROM
• Number Of Bits: 8
• Package Type: 40-pin PDIP
• Programmable Memory: 16K Bytes
• Ram Size: 1K Bytes
• Speed: 33 MHz
• Timers: 4-8-bit, 3-16-bit
• Voltage, Range: 4.5-5.5 V
• Lead Free Status / Rohs Status: RoHS Compliant part Electrostatic Device

PIN DESCRIPTION (continued)
DIP
21
22
23
24
25
26
27
28
10
11
12
13
14
15
16
17
31
—
PLCC
12, 34
PIN
24
25
26
27
28
29
30
31
11
13
14
15
16
17
18
19
35
TQFP
6, 28
18
19
20
21
22
23
24
25
10
11
12
13
29
5
7
8
9
P2.2 (A10)
P2.3 (A11)
P2.4 (A12)
P2.5 (A13)
P2.6 (A14)
P2.7 (A15)
P2.0 (A8)
P2.1 (A9)
NAME
N.C.
P3.0
P3.1
P3.2
P3.3
P3.4
P3.5
P3.6
P3.7
EA
DS87C520/DS83C520 EPROM/ROM High-Speed Microcontrollers
Port 2 (A8–15), I/O. Port 2 is a bidirectional I/O port. The reset
condition of Port 2 is logic high. 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
DS87C520/DS83C520 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 both the
output high and input state. As an alternate function Port 2 can
function as MSB of the external address bus. This bus can be used
to read external ROM and read/write external RAM memory or
peripherals.
Port 3, I/O. Port 3 functions as both an 8-bit, bidirectional I/O
port and an alternate functional interface for External Interrupts,
Serial Port 0, Timer 0 and 1 Inputs, and RD and WR strobes. The
reset condition of Port 3 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 DS87C520/DS83C520 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 both the
output high and input state. The alternate modes of Port 3 are
outlined below.
Port
P3.0
P3.1
P3.2
P3.3
P3.4
P3.5
P3.6
P3.7
External Access Input, Active Low. Connect to ground to force
the DS87C520/DS83C520 to use an external ROM. The internal
RAM is still accessible as determined by register settings. Connect
EA to V
Not Connected. These pins should not be connected. They are
reserved for use with future devices in this family.
6 of 45
CC
Alternate Mode
RXD0
TXD0
INT0
INT1
T0
T1
WR
RD
to use internal ROM.
Serial Port 0 Input
Serial Port 0 Output
External Interrupt 0
External Interrupt 1
Timer 0 External Input
Timer 1 External Input
External Data Memory Write Strobe
External Data Memory Read Strobe
FUNCTION