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HT56R22 Datasheet(PDF) 68 Page - Holtek Semiconductor Inc |
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HT56R22 Datasheet(HTML) 68 Page - Holtek Semiconductor Inc |
68 / 127 page HT56R22/HT56R23/HT56R24/HT56R25/HT56R26 Rev. 1.30 68 December 26, 2014 The status of the SPI interface pins is determined by a number of factors such as whether the device is in the master or slave mode and upon the condition of cer- tain control bits such as CSEN, SIMEN and SCS.In the table I, Z represents an input floating condition. There are several configuration options associated with the SPI interface. One of these is to enable the SIM function which selects the SIM pins rather than normal I/O pins. Note that if the configuration option does not select the SIM function then the SIMEN bit in the SIMCTL0 register will have no effect. Another two SIM configuration options determine if the CSEN and WCOL bits are to be used. Configuration Option Function SIM Function SIM interface or I/O pins SPI CSEN bit Enable/Disable SPI WCOL bit Enable/Disable SPI Interface Configuration Options SPI Registers There are three internal registers which control the over- all operation of the SPI interface. These are the SIMDR data register and two control registers SIMCTL0 and SIMCTL2. Note that the SIMCTL1 register is only used by the I 2C interface. 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 SIMDRregister. 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 POR XXXXXXXX There are also two control registers for the SPI inter- face, SIMCTL0 and SIMCTL2. Note that the SIMCTL2 register also has the name SIMAR which is used by the I 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. Al- though not connected with the SPI function, the SIMCTL0 register is also used to control the Peripheral Clock prescaler. Register SIMCTL2 is used for other control functions such as LSB/MSB selection, write colli- sion flag etc. The following gives further explanation of each SIMCTL1 register bit: · SIMIDLE The SIMIDLE bit is used to select if the SPI interface continues running when the device is in the IDLE mode. Setting the bit high allows the SPI interface to maintain operation when the device is in the Idle mode. Clearing the bit to zero disables any SPI opera- tions when in the Idle mode. This SPI/I 2C idle mode control bit is located at CLKMOD register bit4. · 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. Pin Master/Salve SIMEN=0 Master - SIMEN=1 Slave - SIMEN=1 CSEN=0 CSEN=1 CSEN=0 CSEN=1 SCS=0 CSEN=1 SCS=1 SCS Z ZLZ I, Z I, Z SDO Z OOOO Z SDI Z I, Z I, Z I, Z I, Z Z SCK Z H: CKPOL=0 L: CKPOL=1 H: CKPOL=0 L: CKPOL=1 I, Z I, Z Z Note: ²Z² floating, ²H² output high, ²L² output low, ²I² Input, ²O²output level, ²I,Z² input floating (no pull-high) SPI Interface Pin Status |
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