Danville Signal Processing dspstak 21262sx, User Manual, Page: 21 / 35

Peripheral Microcontroller API
The Peripheral Microcontroller communicates via the SPI bus using a 3 byte packet structure. Flag 1
serves as the SPI slave select line. The SPI bus is bi-directional. Commands are always initiated by
the DSP. The Peripheral Microcontroller only responds. The Peripheral Microcontroller is not a fast
device, as such you must delay transmission of each byte by 15us or more. This gives the Peripheral
Microcontroller time to execute each command.
Most packets will have this form:
Cycle DSP -> PM PM-> DSP
Byte 1 Command Status
Byte 2 Data Echo Command
Byte 3 0x00 Response
Command Summary
Name Description
PM_Cmd_NOP 0x00 No Operation
PM_Cmd_COM_WR 0x01 Transmit a byte from the RS-232 port
PM_Cmd_COM_RD 0x02 Receive a byte from the RS-232 port
PM_Cmd_VERSION 0x03 Firmware version of the Peripheral Microcontroller
PM_Cmd_COM_BAUD 0x04 Set the UART baud rate
PM_Cmd_EE_ADDR 0x05 Set the address of the EE Memory
PM_Cmd_EE_WR 0x06 Write a byte to EE Memory
PM_Cmd_WD 0x07 Watchdog Timeout
PM_Cmd_COM_RESET 0x08 Reset the UART
PM_Cmd_EE_WREN 0x09 Enable Writes to EE Memory
PM_Cmd_RESET 0x0A Reset the dspstak
PM_Cmd_MODE 0x0B Get the dspstak mode setting
PM_Cmd_COM_RTS_CTS 0x0C RS-232 handshaking
PM_Cmd_EE_RD 0x0D Read a byte from EE Memory
-- Reserved 0x0E
PM_Cmd_RESYNC 0x0F Used to resync the Peripheral Microcontroller
-- Reserved >0x0F
dspstak™ 21262sx User Manual
Page 21