EM785830AA

8-bit Micro-controller

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* This specification is subject to be changed without notice.

11

12/1/2004

V1.6

Fig.5 SPI structure

SPIC reg. : SPI control register

SDO: Serial data out

SDI: Serial data in

SCK: Serial clock

RBF : Set by buffer full detector, and reset in software.

RBFI : Interrupt flag. Set by buffer full detector, and reset in software.

Buffer Full Detector : Sets to 1, while an 8-bit shifting is complete.

SE : Loads the data in SPIW register, and begin to shift

SPIE : SPI control register

SPIS reg. : Shifting byte out and in.

The MSB will be shifted first. Both the SPIS register and the SPIW register are loaded at the same time. Once

data being written to, SPIS starts transmission / reception. The received data will be moved to the SPIR

register, as the shifting of the 8-bit data is complete. The RBF (Read Buffer Full ) flag and the RBFI(Read

Buffer Full Interrupt) flag are set.

SPIR reg. : Read buffer.

The buffer will be updated as the 8-bit shifting is complete. The data must be read before the next reception is

finished. The RBF flag is cleared as the SPIR register read.

SPIW reg. : Write buffer.

The buffer will deny any write until the 8-bit shifting is complete. The SE bit will be kept in 1 if the

communication is still under going. This flag must be cleared as the shifting is finished. Users can determine if

the next write attempt is available.

SBR2 ~ SBR0: Programming the clock frequency/rates and sources.

Clock select : Selecting either the internal instruction clock or the external 16.338KHz clock as the shifting clock.

Edge Select : Selecting the appropriate clock edges by programming the SCES bit

SPIS reg.

Read

R5

Write

R5

SPIR reg.

Edge

Select

shift right

bit 0

bit 7

Prescaler

4, 8, 16, 32, 64, 128

PORT62

PORT61

SCK

16.38kHz

SBR2~SBR0

3

Clock Select

2

Noise

Filter

SPIC reg. (R4 page1)

SBR0 ~SBR2

RBF

RBFI

Buffer Full Detector

set to 1

SPIWC

SDO

SPIE

SDI

MUX

SPIE

0

PORT60

MUX

SCK

SPIE

3

SPIW reg.

Edge

Select

MUX

SDI/P74

SDO/P75

SCK/P76