DS87C550 Datasheet, PDF (5/50 Pages) Dallas Semiconductor – EPROM High-Speed Micro with A/D and PWM

PLCC/
CLCC
50-57
57
56
55
54
53
52
51
50
39-46
39
40
41
42
43
44
45
46
24-31
QFP
51-58
58
57
56
55
54
53
52
51
38-42
45-47
38
39
40
41
42
45
46
47
18-20
23-27
SIGNAL NAME
P0.0 (AD0)
P0.1 (AD1)
P0.2 (AD2)
P0.3 (AD3)
P0.4 (AD4)
P0.5 (AD5)
P0.6 (AD6)
P0.7 (AD7)
P2.0 (A8)
P2.1 (A9)
P2.2 (A10)
P2.3 (A11)
P2.4 (A12)
P2.5 (A13)
P2.6 (A14)
P2.7 (A15)
P3.0-P3.7
DS87C550
DESCRIPTION
Port 0-I/O - AD0-7. Port 0 is an open-drain 8-bit, bi-directional general-purpose
I/O port. When used in this mode pullup resistors are required to provide a logic 1
output. As an alternate function, Port 0 operates as a multiplexed address/data bus
to access off-chip memory or peripherals. In this mode, the LSB of the memory
address is output on the bus during the time that ALE is high. When ALE falls to
a logic 0, the port transitions to a bi-directional data bus. In this mode, the port
provides active high drivers for logic 1 output. The reset condition of Port 0 is tri-
state (i.e., the open drain devices are off).
Port 2-I/O Address A15:A8. Port 2 functions as an 8-bit bi-directional I/O port
or alternately as an external address bus (A15-A8). The reset condition of Port 2 is
logic high I/O state. In this state, weak pullups hold the port high allowing the
pins to be used as an input or output as described above for Port 1. As an alternate
function Port 2 can function as MSB of the external address bus. This bus can be
used to read external memory or peripherals.
Port 3 - I/O. Port 3 functions as an 8-bit bi-directional I/O port or alternately as
an interface for External Interrupts, Serial Port 0, Timer 0 & 1 Inputs, and RD and
WR strobes. When functioning as an I/O port, these pins operate as indicated
above for Port 1. The alternate modes of Port 3 are detailed below.
24
18
25
19
26
20
27
23
28
24
29
25
30
26
31
27
7-14
80
1-2
4-8
P4.0-P4.7
Port Alternate Mode
P3.0 RXD0 Serial Port 0 Input
P3.1 TXD0 Serial Port 0 Output
P3.2 INT0
External Interrupt 0
P3.3 INT1
External Interrupt 1
P3.4 T0
Timer 0 External Input
P3.5 T1
Timer 1 External Input
P3.6 WR
External Data Memory Write Strobe
P3.7 RD
External Data Memory Read Strobe
Port 4 - I/O. Port 4 functions as an 8-bit bi-directional I/O port or alternately as
an interface to Timer 2’s Capture Compare functions. When functioning as an I/O
port, these pins operate as indicated in the Port 1 description. The alternate modes
of Port 4 are detailed below.
7
80
8
1
9
2
10
4
11
5
12
6
13
7
14
8
Port 4 Alternate Mode
P4.0 CMSR0 Timer 2 compare match set/reset output 0
P4.1 CMSR1 Timer 2 compare match set/reset output 1
P4.2 CMSR2 Timer 2 compare match set/reset output 2
P4.3 CMSR3 Timer 2 compare match set/reset output 3
P4.4 CMSR4 Timer 2 compare match set/reset output 4
P4.5 CMSR5 Timer 2 compare match set/reset output 5
P4.6 CMT0 Timer 2 compare match toggle output 0
P4.7 CMT1 Timer 2 compare match toggle output 1
5 of 50