Rainbow Electronics AT89LP216 User Manual

Page 51

3621A–MICRO–6/06

AT89LP216 [Preliminary]

Notes:

1. Set up the clock mode before enabling the SPI: set all bits needed in SPCR except the SPE bit, then set SPE.

2. Enable the master SPI prior to the slave device.

3. Slave echoes master on the next Tx if not loaded with new data.

Table 18-1.

SPCR – SPI Control Register

SPCR Address = E9H

Reset Value = 0000 0000B

Not Bit Addressable

SPIE

SPE

DORD

MSTR

CPOL

CPHA

SPR1

SPR0

Bit

Symbol

Function

SPIE

SPI interrupt enable. This bit, in conjunction with the ES bit in the IE register, enables SPI interrupts: SPIE = 1 and ES = 1
enable SPI interrupts. SPIE = 0 disables SPI interrupts.

SPE

SPI enable. SPI = 1 enables the SPI channel and connects SS, MOSI, MISO and SCK to pins P1.4, P1.5, P1.6, and P1.7.
SPI = 0 disables the SPI channel.

DORD

Data order. DORD = 1 selects LSB first data transmission. DORD = 0 selects MSB first data transmission.

MSTR

Master/slave select. MSTR = 1 selects Master SPI mode. MSTR = 0 selects slave SPI mode.

CPOL

Clock polarity. When CPOL = 1, SCK is high when idle. When CPOL = 0, SCK of the master device is low when not
transmitting. Please refer to figure on SPI clock phase and polarity control.

CPHA

Clock phase. The CPHA bit together with the CPOL bit controls the clock and data relationship between master and
slave. Please refer to figure on SPI clock phase and polarity control.

SPR0
SPR1

SPI clock rate select. These two bits control the SCK rate of the device configured as master. SPR1 and SPR0 have no
effect on the slave. The relationship between SCK and the oscillator frequency, F

OSC.

, is as follows:

SPR1

SPR0

SCK

OSC

/32

OSC

/64

Table 18-2.

SPDR – SPI Data Register

SPDR Address = EAH

Reset Value = 00H (after cold reset)
unchanged (after warm reset)

Not Bit Addressable

SPD7

SPD6

SPD5

SPD4

SPD3

SPD2

SPD1

SPD0

Bit