Rainbow Electronics AT89LS53 - Manual (Page 8)

AT89LS53
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Table 4. SPCR—SPI Control Register
SPCR Address = D5H Reset Value = 0000 01XXB
SPIE SPE DORD MSTR CPOL CPHA SPR1 SPR0
Bit 7 6 5 4 3 2 1 0
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 = F
OSC.
divided by
0 0 4
0 1 16
1 0 64
1 1 128
Table 5. SPSR—SPI Status Register
SPSR Address = AAH Reset Value = 00XX XXXXB
SPIF WCOL — — — — — —
Bit 7 6 5 4 3 2 1 0
Symbol Function
SPIF SPI Interrupt Flag. When a serial transfer is complete, the SPIF bit is set and an interrupt is generated if
SPIE = 1 and ES = 1. The SPIF bit is cleared by reading the SPI status register with SPIF and WCOL bits
set, and then accessing the SPI data register.
WCOL Write Collision Flag. The WCOL bit is set if the SPI data register is written during a data transfer. During
data transfer, the result of reading the SPDR register may be incorrect, and writing to it has no effect. The
WCOL bit (and the SPIF bit) are cleared by reading the SPI status register with SPIF and WCOL set, and
then accessing the SPI data register.