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OM5284IB View Datasheet(PDF) - Philips Electronics

Part NameDescriptionManufacturer
OM5284IB CMOS single-chip 8-bit microcontrollers Philips
Philips Electronics Philips
OM5284IB Datasheet PDF : 10 Pages
1 2 3 4 5 6 7 8 9 10
Philips Semiconductors
CMOS single-chip 8-bit microcontrollers
Preliminary specification
OM5234/OM5284
PIN DESCRIPTIONS
PIN NUMBER
MNEMONIC PLCC QFP DIP TYPE NAME AND FUNCTION
VSS
22 6, 16, 20
I Ground: 0V reference. With the QFP package, all VSS pins (VSS1 to VSS4) must be
28, 39
connected.
VDD
44
38
40
I Power Supply: This is the power supply voltage for normal, idle, and power-down
operation.
P0.0–0.7
43–36 37–30 39–32 I/O Port 0: Port 0 is an open-drain, bidirectional I/O port. Port 0 pins that have 1s written to
them float and can be used as high-impedance 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 pull-ups when emitting 1s.
P1.0–P1.7
P1.6
P1.7
2–9 40–44, 1–8
1–3
8
2
7
9
3
8
I/O Port 1: Port 1 is an 8-bit bidirectional I/O port with internal pull-ups, except P1.6 and P1.7,
which are open drain for OM5234 (only). Port 1 pins that have 1s written to them are
pulled high by the internal pull-ups and can be used as inputs. As inputs, port 1 pins that
are externally pulled low will source current because of the internal pull-ups. (See DC
Electrical Characteristics: IIL). Alternate functions include:
I/O
Bidirectional I/O with internal pull-ups (OM5284), and open drain for (OM5234).
I/O
Bidirectional I/O with internal pull-ups (OM5284), and open drain for (OM5234).
P2.0–P2.7 24–31 18–25 21–28 I/O Port 2: Port 2 is an 8-bit bidirectional I/O port with internal pull-ups. Port 2 pins that have
1s written to them are pulled high by the internal pull-ups and can be used as inputs. As
inputs, port 2 pins that are externally being pulled low will source current because of the
internal pull-ups. (See DC Electrical Characteristics: IIL). Port 2 emits the high-order
address byte during fetches from external program memory and during accesses to
external data memory that use 16-bit addresses (MOVX @DPTR). In this application, it
uses strong internal pull-ups when emitting 1s. During accesses to external data memory
that use 8-bit addresses (MOV @Ri), port 2 emits the contents of the P2 special function
register.
P3.0–P3.7 11,
5, 10–17 I/O Port 3: Port 3 is an 8-bit bidirectional I/O port with internal pull-ups. Port 3 pins that have
13–19 7–13
1s written to them are pulled high by the internal pull-ups and can be used as inputs. As
inputs, port 3 pins that are externally being pulled low will source current because of the
pull-ups. (See DC Electrical Characteristics: IIL). Port 3 also serves the special features of
the 80C51 family, as listed below:
11
5
10
I
RxD (P3.0): Serial input port
13
7
11
O
TxD (P3.1): Serial output port
14
8
12
I
INT0 (P3.2): External interrupt
15
9
13
I
INT1 (P3.3): External interrupt
16
10
14
I
T0 (P3.4): Timer 0 external input
17
11
15
I
T1 (P3.5): Timer 1 external input
18
12
16
O
WR (P3.6): External data memory write strobe
19
13
17
O
RD (P3.7): External data memory read strobe
RST
ALE
10
4
33
27
9
I Reset: A high on this pin for two machine cycles while the oscillator is running, resets the
device. An internal diffused resistor to VSS permits a power-on reset using only an
external capacitor to VCC.
30
I/O Address Latch Enable: Output pulse for latching the low byte of the address during an
access to external memory. In normal operation, ALE is emitted at a constant rate of 1/6
the oscillator frequency. Note that one ALE pulse is skipped during each access to
external data memory.
PSEN
32
26
29
O Program Store Enable: Read strobe to external program memory via Port 0 and Port 2.
It is activated twice each machine cycle during fetches from the external program
memory. When executing out of external program memory, two activations of PSEN are
skipped during each access to external data memory. PSEN is not activated (remains
HIGH) during fetches from external program memory. PSEN can sink/source 8 LSTTL
inputs and can drive CMOS inputs without external pull-ups.
EA
35
29
31
I External Access: If during a RESET, EA is held at TTL, level HIGH, the CPU executes
out of the internal program memory ROM provided the Program Counter is less than
16384. If during a RESET, EA is held at TTL LOW level, the CPU executes out of external
program memory. EA is not allowed to float.
XTAL1
21
15
19
I Crystal 1: Input to the inverting oscillator amplifier and input to the internal clock
generator circuits.
XTAL2
20
14
18
O Crystal 2: Output from the inverting oscillator amplifier.
NOTE:
To avoid “latch-up” effect at power-on, the voltage on any pin at any time must not be higher than VDD + 0.5V or VSS – 0.5V, respectively.
1996 Nov 01
4
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