Pepper Computer RS485, RS232 user manual Register Description, Control Register

SMART I/O User’s Manual Chapter 6 Communications Modules

6.2.7 Register Description

The SM-SSI SMART-Module connected to a SMART I/O slot uses the SPI transparent mode for on-board data reading and writing and 5 parallel lines for data selection. On board are a set of registers and peripherals shown in the table below:

N o .	Description	Direction
1	Internal 16-bit Status Register	Read Only
1	Internal 24-bit Control Register	Write Only
1	Internal 8-bit Identification Register	Read Only
1	Internal 24-bit Data Register	Read Only
1	Internal 24-bit Compare Register	Write Only
1	SPI compatible serial EEPROM	Read/Write
1	Optional SPI compatible serial Digital to Analog Converter	Read/Write

Due to the fact that SPI transmissions are full duplex, some read only regis- ters are accessed at the same time as write only registers in order to optimize data transmission. Therefore, when the Control Register is written to, simul- taneously the Status Register is read and similarly when writing to the Compare Register, the Data Register is read.

256 bytes of serial EEPROM contain the module ID number and production data although and further space has been allocated for future use.

6.2.7.1 Control Register

The 24-bit control register is divided into three sub-registers which are cleared after a power-on reset and control:

• FDL: Format Data Length		• AR	: Automatic Reading Mode
• P	: Parity Enable/Disable	• RST : Encoder Reset Control
• ENI : Interrupt Masks		• PT	: Parity Type (Odd/Even)
• SOT: Start Transmission		• DT	: Data Type (Gray/Binary)
• CF	: Data Clock Frequency	• CM : Clear Match output

Page 6- 22 ©1996 PEP Modular Computers GmbH October 01, 1996