Datasheet

© 2008 Microchip Technology Inc. DS22059B-page 39
MCP414X/416X/424X/426X
6.0 SERIAL INTERFACE (SPI)
The MCP4XXX devices support the SPI serial protocol.
This SPI operates in the slave mode (does not
generate the serial clock).
The SPI interface uses up to four pins. These are:
•CS
- Chip Select
• SCK - Serial Clock
• SDI - Serial Data In
• SDO - Serial Data Out
Typical SPI Interfaces are shown in Figure 6-1. In the
SPI interface, The Master’s Output pin is connected to
the Slave’s Input pin and the Master’s Input pin is
connected to the Slave’s Output pin.
The MCP4XXX SPI’s module supports two (of the four)
standard SPI modes. These are Mode
0,0 and 1,1.
The SPI mode is determined by the state of the SCK
pin (V
IH
or V
IL
) on the when the CS pin transitions from
inactive (V
IH
) to active (V
IL
or V
IHH
).
All SPI interface signals are high-voltage tolerant.
FIGURE 6-1: Typical SPI Interface Block Diagram.
SDI/SDO
SDI
SDO
SDO
SDI
R
1
(2)
MCP41X1
SCK
SCK
SDI
SDO
MCP4XXX
SDO
SDI
SCK
SCK
( Master Out - Slave In (MOSI) )
( Master In - Slave Out (MISO) )
Host
Controller
Host
Controller
Typical SPI Interface Connections
Typical MCP41X1 SPI Interface Connections (Host Controller Hardware SPI)
SDI/SDO
SDI
SDO
I/O
MCP41X1
I/O
SCK
Host
Controller
Alternate MCP41X1 SPI Interface Connections (Host Controller Firmware SPI)
(SDO/SDI)
(SCK)
CS
I/O
(1)
CS
I/O
(1)
CS
I/O
(1)
Note 1: If High voltage commands are desired, some type of external circuitry needs to be
implemented.
2: R
1
must be sized to ensure V
IL
and V
IH
of the devices are met.