HT45R37V datasheet(45/90 Pages) HOLTEK

45 / 90 page

HT45R37V

Rev. 1.00

October 20, 2009

The SIMDR register is used to store the data being

transmitted and received. The same register is used by

both the SPI and I

2 C functions. Before the

microcontroller writes data to the SPI bus, the actual

data to be transmitted must be placed in the SIMDR reg-

ister. After the data is received from the SPI bus, the

microcontroller can read it from the SIMDR register. Any

transmission or reception of data from the SPI bus must

be made via the SIMDR register.

Bit

76543210

Label SD7 SD6 SD5 SD4 SD3 SD2 SD1 SD0

R/W

R/W R/W R/W R/W R/W R/W R/W R/W

There are also two control registers for the SPI inter-

face, SIMCTL0 and SIMCTL2. Note that the SIMCTL2

2C function. The SIMCTL1 register is not used by the

SPI function, only by the I

2C function. Register

SIMCTL0 is used to control the enable/disable function

and to set the data transmission clock frequency. Regis-

ter SIMCTL2 is used for other control functions such as

LSB/MSB selection, write collision flag etc. The

SIMIDLE bit in the CLKMOD register is used to select if

the SIM continues running when the device is in the

IDLE mode. Setting the bit high allows the SIM to main-

tain operation when the device is in the Idle mode.

Clearing the bit to zero disables any SIM operations

when in the Idle mode.

The following gives further explanation of each

SIMCTL1 register bit:

· SIMEN

The bit is the overall on/off control for the SPI inter-

face. When the SIMEN bit is cleared to zero to disable

the SPI interface, the SDI, SDO, SCK and SCS lines

will be in a floating condition and the SPI operating

current will be reduced to a minimum value. When the

bit is high the SPI interface is enabled. The SIMconfig-

uration option must have first enabled the SIM inter-

face for this bit to be effective. Note that when the

SIMEN bit changes from low to high the contents of

the SPI control registers will be in an unknown condi-

tion and should therefore be first initialised by the ap-

plication program.

· SIM0~SIM2

These bits setup the overall operating mode of the SIM

function. As well as selecting if the I

2C or SPI function,

they are used to control the SPI Master/Slave selec-

tion and the SPI Master clock frequency. The SPI

clock is a function of the system clock but can also be

chosen to be sourced from the Timer/Event Counter. If

the SPI Slave Mode is selected then the clock will be

supplied by an external Master device.

SIM0

SIM1

SIM2

SPI Master/Slave Clock

Control and I2C Enable

SPI Master, fSYS/4

SPI Master, fSYS/16

SPI Master, fSYS/64

SPI Master, fSUB

100

SPI Master Timer/Event

Counter 0 output/2

SPI Slave

110

2C mode

Not used

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