MIKROE-419 mikroElektronika, MIKROE-419 Datasheet - Page 26

• Manufacturer Part Number: MIKROE-419
• Description: Development Boards & Kits - PIC / DSPIC BIGPIC6 DEVELOPMENT SYSTEM
• Manufacturer: mikroElektronika

Specifications of MIKROE-419

• Rohs: yes
• Product: Development Kits
• Core: PIC
• Interface Type: ICD, IDC10, JTAG, RS-232, USB
• Operating Supply Voltage: 9 V to 32 V
• Data Bus Width: 8 bit
• Description/function: Development Board Only, Touch Screen, Pencil, DS1820, LCD, Serial Cable, GLCD not included
• Dimensions: 265 mm x 220 mm
• For Use With: PIC

26
Figure 20-1: Port expander
MikroElektronika
20.0.
20.0. Port Expander
The SPI communication lines and MCP23S17 circuit provide the BigPIC6 development system with a means of increasing the
number of available I/O ports by two. If the port expander communicates to the microcontroller over the DIP switch SW11 then the
microcontroller pins RE0, RE1, RC5, RC4 and RC3, used for the operation of port expander, cannot be used as I/O pins.
Figure 20-3: Port expander schematic
VCC
Port Expander (Additional Input/Output Ports)
RH2
RH3
RE1
RE0
RG0
RG1
RG2
RG3
MCLR
RG4
GND
VCC
RF7
RF6
RF5
RF4
RF3
RF2
RH7
RH6
PIC18Fxx
VCC
LD86
P1.7
Figure 20-2: Position of DIP
switch SW11 when port
expander is enabled
LD85
P1.6
Jumper for selecting
pull-up/pull-down resistor
PORT0
PORT1
VCC
(Additional Input/Output Ports)
LD84
P1.5
LD83
P1.4
OSC2
OSC1
GND
VCC
RB0
RB1
RB2
RB3
RB4
RB5
RB6
RB7
RC5
RC4
RC3
RC2
RJ2
RJ3
RJ7
RJ6
LD82
P1.3
8x2K2
VCC
LD81
P1.2
P0_LED
P1_LED
The microcontroller communicates to the port expander (MCP23S17 circuit)
using serial communication (SPI). The advantage of such communication is that
only fi ve lines are used for transmitting and receiving data simultaneously:
MOSI
MISO
SCK
CS
RST
Data transfer is performed in both directions simultaneously by means of
MOSI and MISO lines. The MOSI line is used for transferring data from the
microcontroller to the port expander, whereas the MISO line transfers data from
the port expander to the microcontroller. The microcontroller initializes data
transfer when the CS pin is driven low (0V). It causes the microcontroller to send
clock signal (SCK) and therefore starts data exchange. The principle of operation
of the port expander’s ports 0 and 1 is almost identical to the operation of other
ports on the development system. The only difference here is that port signals are
received in parallel format. The MCP23S17 converts then such signals into serial
format and sends them to the microcontroller. The result is a reduced number of
lines used for sending signals from ports 0 and 1 to the microcontroller.
J15
RC5
RC4
RC3
8x10K
RE0
RN20
RE1
VCC
SW11
LD80
P1.1
VCC
P1.0
P1.2
P1.4
P1.6
- Master Output, Slave Input (microcontroller output, MCP23S17 input)
- Master Input, Slave Output (microcontroller input, MCP23S17 output)
- Serial Clock (microcontroller clock signal)
- Chip Select (enables data transfer)
- Reset
LD79
P1.0
RN21
PE-
PE-
SPI-MOSI
SPI-MISO
SPI-SCK
PORT1
CN11
CS#
RST
P1.1
P1.3
P1.5
P1.7
VCC
R17
100K
SPI-MOSI
SPI-MISO
VCC
SPI-SCK
RN22
PE-CS#
P1.0
P1.1
P1.2
P1.3
P1.4
P1.5
P1.6
P1.7
U7
MCP23S17
LD78
GPB0
GPB1
GPB2
GPB3
GPB4
GPB5
GPB6
GPB7
SCK
SI
SO
VCC
GND
CS
P0.7
LD77
P0.6
BigPIC6 Development System
BigPIC6 Development System
RESET
GPA7
GPA6
GPA5
GPA4
GPA3
GPA2
GPA1
GPA0
INTB
INTA
GND
GND
GND
8x2K2
LD76
P0.5
P0.7
P0.6
P0.5
P0.4
P0.3
P0.2
P0.1
P0.0
PE-RST
LD75
P0.4
LD74
P0.3
VCC
P0.0
P0.2
P0.4
P0.6
PORT0
CN10
LD73
P0.2
DIP switch
SW11 enables
port expander
P0.1
P0.3
P0.5
P0.7
LD72
P0.1
8x10K
VCC
RN19
LD71
P0.0
J14