13
PC Software
UART Support, PSDload
PSDload is a PC application (WIN95/98/NT) which allows serial communications between the PC and the
ST series of Development Boards. This application utilizes the microcontroller UART on the target
system side and a standard serial PC channel. The protocol utilizes commands to perform the following
functions on the resident PSD, and potentially, other Eval Board resources.
1. Read and write registers, memory
2. Erase and fill memory areas
3. Write to the LCD display
4. Download files from the PC to the target system(any system area)
5. Program the downloaded file into the PSD memory in circuit(MAIN or BOOT areas)
6. Upload files from the PSD or development board resources
7. Reset the target system.
The primary target of this interface is FLASH based PSDs from the standpoint of in circuit programmability.
However, the capability is also applicable to the OTP family of PSDs(note that in circuit programming is not
available due to the OTP families EPROM base).
Definition of Terms
A few term definitions will ease the understandability of the document.
a. PSD
Load
is the windows interface running on the PC.
b. PSD
Step
is the protocol used to communicate between the PC and the Evaluation board. (Simple
Test and Evaluation Protocol).
Serial Interface
The connection from the PC to the evaluation board is via a standard 9 pin null modem cable. The
communications parameters are 8 data bits, 1 stop bit and no parity. The interface uses simple three wire (TX,
Rx and GND) RS-232 with full-duplex operations. Flow control is accomplished via software handshaking
incorporated into the protocol (this is not XON XOFF). The baud rate of PSDload is selectable from 4.8k to
56k but the 8032 board is presently restricted to 19.2kbaud. Software flow control is used in order to minimize
the master/slave physical connections.
Each command sent from PSDload is intended to elicit a response from the Evaluation Board. This handshake
is used to verify a valid receipt of the transaction. Two methods exist to terminate this handshake if it should
become disrupted for any reason; the first is a hot key inside PSDload,
timeout parameter entered on comm screen.
and the second is a communications
PSD Architecture
The PSD contains several different blocks of memory which vary within each family and between the families.
These encompass the following memory types; EPROM, FLASH, EEPROM, SRAM, and registers.
Generically these memory blocks are termed a memory
region
. The PSD913 contains 128kx8 FLASH,
32kx8 FLASH and 2kx8 sram.
PSDLoad must be aware of how these regions map into the system memory as all operations occur based on
addresses associated with the system memory. The system memory map is determined using the development
tool, PSDsoft Express. This information is provided in the form of a *.mmf file automatically generated from
PSDsoft Express and requested by PSDload at invocation. PSDload utilizes this information to portray the
system memory map to the user and construct commands to send to the Eval Board.
Since the system memory map is utilized to achieve the download, the PLD within the PSD must have been
programmed prior to a serial download attempt. PLD programming is accomplished via either the JTAG
interface or with a conventional parallel programmer, both of which are external to PSDstep/PSDload.