PIC18F13K50-E/P MICROCHIP [Microchip Technology], PIC18F13K50-E/P Datasheet - Page 142

• Manufacturer Part Number: PIC18F13K50-E/P
• Manufacturer: MICROCHIP [Microchip Technology]

PIC18F1XK50/PIC18LF1XK50
15.2.5
The master can initiate the data transfer at any time
because it controls the SCK. The master determines
when the slave (Processor 2, Figure 15-2) is to
broadcast data by the software protocol.
In Master mode, the data is transmitted/received as
soon as the SSPBUF register is written to. If the SPI is
only going to receive, the SDO output could be dis-
abled (programmed as an input). The SSPSR register
will continue to shift in the signal present on the SDI pin
at the programmed clock rate. As each byte is
received, it will be loaded into the SSPBUF register as
if a normal received byte (interrupts and status bits
appropriately set).
FIGURE 15-3:
DS41350C-page 140
Write to
SSPBUF
SCK
(CKP = 0
CKE = 0)
SCK
(CKP = 1
CKE = 0)
SCK
(CKP = 0
CKE = 1)
SCK
(CKP = 1
CKE = 1)
SDO
(CKE = 0)
SDO
(CKE = 1)
SDI
(SMP = 0)
Input
Sample
(SMP = 0)
SDI
(SMP = 1)
Input
Sample
(SMP = 1)
SSPIF
SSPSR to
SSPBUF
MASTER MODE
SPI MODE WAVEFORM (MASTER MODE)
bit 7
bit 7
bit 7
bit 7
bit 6
bit 6
bit 5
bit 5
Preliminary
bit 4
bit 4
bit 3
bit 3
The clock polarity is selected by appropriately
programming the CKP bit of the SSPCON1 register.
This
communication as shown in Figure 15-3, Figure 15-5
and Figure 15-6, where the MSB is transmitted first. In
Master mode, the SPI clock rate (bit rate) is user
programmable to be one of the following:
• F
• F
• F
• Timer2 output/2
This allows a maximum data rate (at 64 MHz) of
16.00 Mbps.
Figure 15-3 shows the waveforms for Master mode.
When the CKE bit is set, the SDO data is valid before
there is a clock edge on SCK. The change of the input
sample is shown based on the state of the SMP bit. The
time when the SSPBUF is loaded with the received
data is shown.
OSC
OSC
OSC
then,
/4 (or T
/16 (or 4 • T
/64 (or 16 • T
bit 2
bit 2
CY
would
)
bit 1
bit 1
CY
CY
)
)
© 2009 Microchip Technology Inc.
give
bit 0
bit 0
bit 0
bit 0
waveforms
4 Clock
Modes
for
SPI