Datasheet

© 2007 Microchip Technology Inc. DS39599G-page 163
PIC18F2220/2320/4220/4320
17.3.8 MASTER IN POWER-MANAGED
MODES
In Master mode, module clocks may be operating at a
different speed than when in full-power mode, or in the
case of the power-managed Sleep mode, all clocks are
halted.
In most power-managed modes, a clock is provided
to the peripherals and is derived from the primary
clock source, the secondary clock (Timer1 oscillator
at 32.768 kHz) or the internal oscillator block (one of
eight frequencies between 31 kHz and 8 MHz). See
Section 2.7 “Clock Sources and Oscillator
Switching” for additional information.
In most cases, the speed that the master clocks SPI
data is not important; however, this should be
evaluated for each system.
If MSSP interrupts are enabled, they can wake the con-
troller from a power-managed mode when the master
completes sending data. If an exit from a power-
managed mode is not desired, MSSP interrupts should
be disabled.
If the Sleep mode is selected, all module clocks are
halted and the transmission/reception will pause until
the device wakes from the power-managed mode.
After the device returns to full-power mode, the module
will resume transmitting and receiving data.
17.3.8.1 Slave in Power-Managed Modes
In Slave mode, the SPI Transmit/Receive Shift register
operates asynchronously to the device. This allows the
device to be placed in any power-managed mode and
data to be shifted into the SPI Transmit/Receive Shift
register. When all 8 bits have been received, the MSSP
interrupt flag bit will be set and if MSSP interrupts are
enabled, will wake the device from a power-managed
mode.
17.3.9 EFFECTS OF A RESET
A Reset disables the MSSP module and terminates the
current transfer.
17.3.10 BUS MODE COMPATIBILITY
Table 17-1 shows the compatibility between the
standard SPI modes and the states of the CKP and
CKE control bits.
TABLE 17-1: SPI BUS MODES
There is also an SMP bit which controls when the data
is sampled.
TABLE 17-2: REGISTERS ASSOCIATED WITH SPI OPERATION
Standard SPI Mode
Terminology
Control Bits State
CKP CKE
0, 0 0 1
0, 1 0 0
1, 0 1 1
1, 1 1 0
Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
Value on
POR, BOR
Value on
all other
Resets
INTCON GIE/GIEH PEIE/
GIEL
TMR0IE INT0IE RBIE TMR0IF INT0IF RBIF 0000 000x 0000 000u
PIR1
PSPIF
(1)
ADIF RCIF TXIF SSPIF CCP1IF TMR2IF TMR1IF 0000 0000 0000 0000
PIE1
PSPIE
(1)
ADIE RCIE TXIE SSPIE CCP1IE TMR2IE TMR1IE 0000 0000 0000 0000
IPR1
PSPIP
(1)
ADIP RCIP TXIP SSPIP CCP1IP TMR2IP TMR1IP 1111 1111 1111 1111
TRISC PORTC Data Direction Register 1111 1111 1111 1111
SSPBUF MSSP Receive Buffer/Transmit Register xxxx xxxx uuuu uuuu
SSPCON1 WCOL SSPOV SSPEN CKP SSPM3 SSPM2 SSPM1 SSPM0 0000 0000 0000 0000
TRISA
TRISA7
(1)
TRISA6
(1)
PORTA Data Direction Register --11 1111 --11 1111
SSPSTAT SMP CKE
D/A P S R/W UA BF 0000 0000 0000 0000
Legend: x = unknown, u = unchanged, - = unimplemented, read as ‘0’. Shaded cells are not used by the MSSP in SPI mode.
Note 1: The PSPIF, PSPIE and PSPIP bits are reserved on the PIC18F2X20 devices; always maintain these bits clear.