PIC16F688

Manufacturer Part NumberPIC16F688
ManufacturerMicrochip Technology Inc.
PIC16F688 datasheet
 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
Page 31
32
Page 32
33
Page 33
34
Page 34
35
Page 35
36
Page 36
37
Page 37
38
Page 38
39
Page 39
40
Page 40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
Page 35/202:

PORTA and the TRISA Registers

Download datasheet (4Mb)Embed
PrevNext
4.0
I/O PORTS
There are as many as twelve general purpose I/O pins
available. Depending on which peripherals are enabled,
some or all of the pins may not be available as general
purpose I/O. In general, when a peripheral is enabled,
the associated pin may not be used as a general
purpose I/O pin.
4.1

PORTA and the TRISA Registers

PORTA is a 6-bit wide, bidirectional port. The
corresponding data direction register is TRISA. Setting
a TRISA bit (= 1) will make the corresponding PORTA
pin an input (i.e., put the corresponding output driver in
a High-Impedance mode). Clearing a TRISA bit (= 0)
will make the corresponding PORTA pin an output (i.e.,
put the contents of the output latch on the selected pin).
The exception is RA3, which is input only and its TRISA
bit will always read as ‘1’. Example 4-1 shows how to
initialize PORTA.
Reading the PORTA register reads the status of the
pins, whereas writing to it will write to the PORT latch.
All write operations are read-modify-write operations.
REGISTER 4-1:
PORTA: PORTA REGISTER
U-0
U-0
R/W-x
RA5
bit 7
Legend:
R = Readable bit
W = Writable bit
-n = Value at POR
‘1’ = Bit is set
bit 7-6
Unimplemented: Read as ‘0’
bit 5-0
RA<5:0>: PORTA I/O Pin bit
1 = Port pin is > V
IH
0 = Port pin is < V
IL
REGISTER 4-2:
TRISA: PORTA TRI-STATE REGISTER
U-0
U-0
R/W-1
TRISA5
bit 7
Legend:
R = Readable bit
W = Writable bit
-n = Value at POR
‘1’ = Bit is set
bit 7-6
Unimplemented: Read as ‘0’
bit 5-0
TRISA<5:0>: PORTA Tri-State Control bits
1 = PORTA pin configured as an input (tri-stated)
0 = PORTA pin configured as an output
Note 1:
TRISA<3> always reads ‘1’.
2:
TRISA<5:4> always reads ‘1’ in XT, HS and LP Oscillator modes.
© 2007 Microchip Technology Inc.
Therefore, a write to a port implies that the port pins are
read, this value is modified and then written to the
PORT data latch. RA3 reads ‘0’ when MCLRE = 1.
The TRISA register controls the direction of the
PORTA pins, even when they are being used as analog
inputs. The user must ensure the bits in the TRISA
register are maintained set when using them as analog
inputs. I/O pins configured as analog input always read
‘0’.
Note:
The ANSEL and CMCON0 registers must
be initialized to configure an analog
channel as a digital input. Pins configured
as analog inputs will read ‘0’.
EXAMPLE 4-1:
INITIALIZING PORTA
BANKSEL PORTA
CLRF
PORTA
MOVLW
07h
MOVWF
CMCON0
BANKSEL ANSEL
CLRF
ANSEL
MOVLW
0Ch
MOVWF
TRISA
R/W-0
R-x
R/W-0
RA4
RA3
RA2
U = Unimplemented bit, read as ‘0’
‘0’ = Bit is cleared
R/W-1
R-1
R/W-1
TRISA4
TRISA3
TRISA2
U = Unimplemented bit, read as ‘0’
‘0’ = Bit is cleared
PIC16F688
;
;Init PORTA
;Set RA<2:0> to
;digital I/O
;
;digital I/O
;Set RA<3:2> as inputs
;and set RA<5:4,1:0>
;as outputs
R/W-0
R/W-0
RA1
RA0
bit 0
x = Bit is unknown
R/W-1
R/W-1
TRISA1
TRISA0
bit 0
x = Bit is unknown
DS41203C-page 33