;======================================================================= ;======================================================================= ; SERIAL PERIPHERAL INTERFACE (SPI) DRIVER ; SPI_ML ; Revision 1.01, 07.05.98 ; Developed by Authentic Engineering for Scenix Semiconductor, Inc. ; Authentic Engineering // http://www.authenticeng.com // ak@silcom.com ; ;======================================================================= ; MASTER MODE LOW RATE SPI DRIVER. SINGLE MASTER CONFIGURATION ; ; This driver provides SPI interface to realtively slow devices. ; The data are transfered by words. Word length is software configurable ; from 1 to 16 bits. ; This driver is a part of a set of SX SPI drivers. It makes use of general ; set of control and status data, developed for the entire family of drivers ; ; CLOCK RATE ; ; The SPI clock rate is driven by the system RTCC. ; Minimum clock rate is limited by the RTCC prescaler setting which should be ; configured by the user. When the RTCC is configured to the minimum rate and ; prescaler is set to 1:2, the SPI clock rate will be equal to 10.2 microsec. ; With the prescaler setting at 1:256 the minimum clock rate will be 1.3056 millisec. ; Maximum clock rate can be achived at RTCC prescaler setting 1:2 ; and RTCC reload register - $80. Desierable configuration of the RTCC prescaler ; must be determined by the user. ; ; Clock (SCLK) PHASE and POLARITY are software configurable. ; ; There are FOUR basic signal lines associated with the SPI protocol: ; Master-Out-Slave-In MOSI signal line ; Master-In-Slave_Out MISO signal line ; Serial Clock SCLK signal line ; Slave Select SS signal line ; Arbitrary pins of the SX-28 can be used for current driver ; ;============================================================================== ; ; INITIALIZATION OF SPI DRIVER ; ; USER program must: ; 1. Provide appropriate configuration of the SX-28 ports. ; ; 2. Define next parameters: ; ; SPI_RAM_BANK - to define the origin in SX RAM banks ; SPI_CLOCK_RATE - to define the clock rate. This byte is used by the driver ; as the RTCC reload register value ; SPI_COMMAND - command and configuration byte. This byte defines: ; - SPI Clock polarity ; - Mode (Master or Slave) ; - Speed (Fast or Slow) ; - Direction (Read/Write) ; - Word Lenght (1 to 16). ; Driver will set the RTCC reload value to the SPI_CLOCK_RATE. The USER ; program must take care about restoration of the RTCC reload value, after ; the SPI driver will complete its operation. ; ; Current driver support only Master Mode and Slow Speed data transfer. ; ; The driver supports 5 commands, specified by the 4 MSBs of the SPI_COMMAND byte ; $0 RESET ; $2 GET WORD in MASTER mode, define FALLING edge ; $6 GET WORD in MASTER mode, define RISING edge ; $A SEND WORD in MASTER mode, define FALLING edge ; $E SEND WORD in MASTER mode, define RISING edge ; Generally for the SPI interface there is no diffrence between GET and SEND, ; however it seems convinient to have different commands, because it allows to customize ; transmit and receive cycles for specific peripherals. Such an examle is presented in Demo #1. ; ; Four LSBs of SPI_COMMAND byte are used for word length definition. ; ; $1 corresponds to one bit length ; ... ; $F corresponds to fifteen bit legth ; $0 corresponds to sixteen bit length ; ; For example, SPI_COMMAND for 12 bit data transfer to the peripheral looks like - $EC ; ; 3. Driver is driven by RTCC interrupts. In order to start data transfer USER program ; must: ; - check that SPI_BUSY flag is cleared ; - set SPI_CLOCK_RATE and SPI_COMMAND ; - enable timer interrupts ; - perform JMP SPI_ENTRY when RTCC interrupt occures ; See example in DEMO #1 ;============================================================================================= ; ; The SPI_STATUS byte provides the information on driver status. It consists of a set of ; flags, described in the comments to the code. ; ; ; SX-28 pin assignment presented below is an example used in 'SPI DEMO #1' ; program. ;======================= CODE START device pins28, pages4,banks8 device turbo, stackx, optionx id 'SPI_ML' ;======================= PIN ASSIGNMENT ;======== example of pin assignment used in DEMO #1 spi_clk_pin = rb.0 ;SPI clock line spi_out_pin = rb.1 ;master_in slave_out line spi_in_pin = rb.2 ;master_out slave_in line spi_ADC_cs_pin = rb.4 ;slave select (ADC) spi_DAC_cs_pin = rb.5 ;slave select (DAC) ;======================== SPI DEVICE RAM ORIGIN org 10h ;example of RAM bank assignment spi_ram_bank = $ spi_command ds 1 bit_wide_0 equ spi_command.0 ;the word length LSB bit_wide_1 equ spi_command.1 ;1_st bit bit_wide_2 equ spi_command.2 ;2_nd bit bit_wide_3 equ spi_command.3 ;the word length MSB fast_ON equ spi_command.4 ;set if FAST MODE master_ON equ spi_command.5 ;set if MASTER MODE rising_ON equ spi_command.6 ;set if RISING EDGE transmit_ON equ spi_command.7 ;set if TRANSMIT ;======================= SPI_STATUS byte spi_status ds 1 spi_ready equ spi_status.0 ;SET when driver is ready (has been initialized) spi_busy equ spi_status.1 ;set when data transfer is active ;spi_master equ spi_status.2 ;SET when SPI master is inited ;spi_slave equ spi_status.3 ;SET when SPI slave is inited spi_command_ERR equ spi_status.4 ;set when command byte containes not supported command spi_tx_complete equ spi_status.5 ;transmit complete spi_rx_complete equ spi_status.6 ;receive complete ;spi_error equ spi_status.7 ;SET when transmit is not finished correctly ;spi_rx_complete and spi_tx_complete flags are needed when two different SS lines were inited simultaneously ;and receive and transmit are controled in the same time. Otherwise, this flag is not extended ;(see SPI_M, SPI_S SPI drivers). ;======================= SPI_STATE byte spi_state ds 1 spi_ms_ON equ spi_state.0 ;set when Master Mode spi_sl_ON equ spi_state.1 ;set when Slave Mode spi_rx_ON equ spi_state.2 ;set when Receive Mode spi_tx_ON equ spi_state.3 ;set when Transmit Mode spi_clk_state equ spi_state.4 ;state of the SPI_CLOCK line; ;spi_timer_IRQ_ON equ spi_state.5 ;SPI transfer under timer IRQ :indicated by rc.0 ;spi_port_IRQ_ON equ spi_state.6 ;SPI transfer under port IRQ :indicated by rc.2 ;======================= SPI_CLOCK byte spi_clk_rate ds 1 ;RTCC reload value spi_buff ds 1 ;SPI I/O shift register (MSByte) spi_buff_low ds 1 ;SPI I/O shift register (LSByte) spi_shift_counter ds 1 ;shift counter spi_bits_total ds 1 ;number of bits to transfer spi_shifts_init ds 1 ;number of initial shifts before transfer spi_clk_counter ds 1 ;used only for DEMO #1 with LTC1594 spi_clks_init ds 1 ;used only for DEMO #1 with LTC1594 ;======================= INTERRUPT START spi_entry bank spi_ram_bank ;SPI driver entry point jb master_ON,master_entry snb rising_ON setb spi_command_ERR ;return from interrupt if wrong command snb transmit_ON setb spi_command_ERR clr spi_command setb spi_ready mov w,spi_clk_rate retiw ;======================= SPI MASTER ENTRY master_entry test spi_shift_counter ;test if this is first entry jnz :master_start :init_master jb spi_ms_ON,:ms_rx_finish ;initialization of the driver (on the first entry) setb spi_busy_ON setb spi_ms_ON sb transmit_ON setb spi_rx_ON snb transmit_ON setb spi_tx_ON snb spi_rx_ON clrb spi_ADC_cs_pin ;this is an example to show how ;generate CS signals for a specific ;peripherals. This is CS for ADC snb spi_tx_ON clrb spi_DAC_cs_pin ;CS for DAC sb rising_ON ;set the SPI_CLK polarity clrb clk_state snb rising_ON setb clk_state sb rising_ON clrb spi_clk_pin snb rising_ON setb spi_clk_pin mov w,spi_command ;set the number of bits to transfer and w,#%00001111 mov spi_bits_total,w mov w,spi_command or w,#%11110000 mov spi_shifts_init,w not spi_shifts_init inc spi_shifts_init mov spi_shift_counter,spi_bits_total clc rl spi_shift_counter mov spi_clk_counter,spi_clks_init ;Example for LTC1594 ADC only clc ;LTC1594 input MX control rl spi_clk_counter ;end of LTC1594 part :set_bit_position test spi_shifts_init ;initial shift before transfer clc ;needed to put MSB of the word to sz ;bit.7 SPI_BUFF position rl spi_buff_low sz rl spi_buff sz djnz spi_shifts_init,:set_bit_position jmp :master_exit ;initialization done, first interrupt exit ;=============================================== Example of the LTC1594 driver :master_start nop test spi_clk_counter ;Example for LTC1594 ADC only jz :master_rx ;Jump to normal master receive xor rb,#%00000001 ;LTC1594 input MX control dec spi_clk_counter ;sclk ADC UP/DOWN jmp :master_exit ;interrupt exit for the ADC MX control ;=============================================== End of ltc1594 example :master_rx jb clk_state,:master_tx ;bit reception from SPI_IN_PIN movb c,spi_in_pin rl spi_buff_low rl spi_buff setb spi_clk_pin dec spi_shift_counter setb clk_state jmp :master_exit ;bit received :master_tx movb spi_out_pin,spi_buff.7 ;bit transmit clrb spi_clk_pin dec spi_shift_counter clrb clk_state jmp :master_exit ;bit transmitted :ms_rx_finish sb spi_rx_ON ;reception completed jmp :ms_tx_finish setb spi_rx_complete ;correct reception finished setb spi_ADC_cs_pin ;disable ADC CS clrb spi_rx_ON jmp :master_finish :ms_tx_finish setb spi_DAC_cs_pin ;disable DAC CS clrb spi_tx_ON ;transmission completed setb spi_tx_complete jmp :master_finish :master_finish clrb spi_ms_ON clr spi_command clrb spi_busy_ON :master_exit mov w,spi_clk_rate retiw ;======================= END OF MASTER MODE SLOW SPI DRIVER
| file: /Techref/scenix/spi_ml.src, 9KB, , updated: 1999/2/20 12:23, local time: 2024/11/8 13:43,
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Ashley Roll has put together a really nice little unit here. Leave off the MAX232 and keep these handy for the few times you need true RS232! |
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