PIC18C242 MICROCHIP [Microchip Technology], PIC18C242 Datasheet - Page 125

• Manufacturer Part Number: PIC18C242
• Description: High-Performance Microcontrollers with 10-Bit A/D
• Manufacturer: MICROCHIP [Microchip Technology]

14.2.1.5
In slave mode, the data is transmitted and received as
the external clock pulses appear on SCK. When the
last bit is latched, the SSPIF interrupt flag bit is set.
While in slave mode the external clock is supplied by
the external clock source on the SCK pin. This external
clock must meet the minimum high and low times as
specified in the electrical specifications.
While in sleep mode, the slave can transmit/receive
data. When a byte is receive the device will wake-up
from sleep.
14.2.1.6
The SS pin allows a synchronous slave mode. The
SPI must be in slave mode with SS pin control
enabled (SSPCON1<3:0> = 04h). The pin must not
be driven low for the SS pin to function as an input.
The Data Latch must be high. When the SS pin is
low, transmission and reception are enabled and
the SDO pin is driven. When the SS pin goes high,
FIGURE 14-4: SLAVE SYNCHRONIZATION WAVEFORM
SS
SCK
(CKP = 0
CKE = 0)
SCK
(CKP = 1
CKE = 0)
Write to
SSPBUF
SDO
SDI
(SMP = 0)
Input
Sample
(SMP = 0)
SSPIF
Interrupt
Flag
SSPSR to
SSPBUF
7/99 Microchip Technology Inc.
SLAVE MODE
SLAVE SELECT SYNCHRONIZATION
bit7
bit7
bit6
Preliminary
the SDO pin is no longer driven, even if in the mid-
dle of a transmitted byte, and becomes a floating
output. External pull-up/ pull-down resistors may be
desirable, depending on the application.
When the SPI module resets, the bit counter is forced
to 0. This can be done by either by forcing the SS pin to
a high level or clearing the SSPEN bit.
To emulate two-wire communication, the SDO pin can
be connected to the SDI pin. When the SPI needs to
operate as a receiver the SDO pin can be configured as
an input. This disables transmissions from the SDO.
The SDI can always be left as an input (SDI function)
since it cannot create a bus conflict.
Note 1: When the SPI is in Slave Mode with SS pin
Note 2: If the SPI is used in Slave Mode with CKE
control enabled, (SSPCON<3:0> = 0100)
the SPI module will reset if the SS pin is
set to V
set, then the SS pin control must be
enabled.
bit7
bit7
DD
.
PIC18CXX2
Next Q4 cycle
after Q2
DS39026B-page 125
bit0
bit0