USING THE TEST-ROM ROUTINES
17.7 RISM COMMAND DESCRIPTIONS
Table 17-7 lists and describes all the RISM commands for both the serial port mode and SDU RISM execution routines, along with their associated opcodes. Some of the RISM commands listed in Table 17-7 are SDU RISM only and some are serial port RISM only. Also, the RISM commands that are shared between the SDU and serial port do not share the same opcode values.
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Table 17-7. RISM Commands |
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Serial |
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Command |
Port |
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SDU |
Description |
RISM |
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RISM |
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Opcode |
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Opcode |
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SET_DLE_FLAG |
00H |
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— |
Sets the DLE (data latch enable) flag in bit 0 of the MODE |
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register (57H) to tell the RISM that the next byte on the |
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serial port is data that should be loaded into the DATA |
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register (58H). The flag is cleared as soon as the byte is |
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read. |
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RISM_IDLE |
— |
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00H |
The RISM routine halts and enters a loop waiting for |
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another interrupt. |
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TRANSMIT |
02H |
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— |
Transmits the low byte of the DATA register to the serial |
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port through the CHAR register, shifts the DATA register |
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right (long) by eight bits, and increments ADDR by one. |
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READ_BYTE |
04H |
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01H |
Reads the byte contents of the memory address pointed |
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to by the RISM_ADDR register and puts it into the low |
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byte of the DATA register (location 403H in SDU RISM |
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execution). The shadow address register, located in |
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register RAM, is loaded with RISM_ADDR + 1. |
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READ_WORD |
05H |
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02H |
Reads the word contents of the memory address pointed |
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to by the RISM_ADDR register and puts it into the low |
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word of the DATA register (locations 402–403H in SDU |
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RISM execution). The shadow address register, located |
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in register RAM, is loaded with RISM_ADDR + 2. |
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WRITE_BYTE |
07H |
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03H |
Stores the byte contents of the RISM_DATA register in |
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the memory address pointed to by the shadow address |
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register and increments the shadow address register by |
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one. |
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WRITE_WORD |
08H |
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04H |
Stores the word contents of the RISM_DATA register in |
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the memory address pointed to by the shadow address |
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register and increments the shadow address register by |
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two. |
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DATA_TO_ADDR |
0AH |
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— |
Puts the low word of the DATA register into the ADDR |
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register. |
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GO |
12H |
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05H |
Starts execution at location pointed to by register RAM |
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address 60H. |
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HALT |
13H |
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06H |
Stops execution and returns to the Monitor_Pause state |
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(RISM_IDLE state in SDU RISM execution). |
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— indicates the RISM command is not available |
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17-15
8XC196EA USER’S MANUAL
Table 17-7. RISM Commands (Continued)
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Serial |
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Command |
Port |
SDU |
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Description |
RISM |
RISM |
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Opcode |
Opcode |
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READ_NEXT_BYTE |
— |
11H |
Reads the byte contents of the next memory address |
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pointed to by the shadow address register and |
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increments by one. |
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READ_NEXT_WORD |
— |
12H |
Reads the word contents of the next memory address |
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pointed to by the shadow address register and |
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increments by two. |
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WRITE_NEXT_BYTE |
— |
13H |
Stores the byte contents of the next memory address |
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pointed to by the shadow address register and |
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increments by one. |
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WRITE_NEXT_WORD |
— |
14H |
Stores the word contents of the next memory address |
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pointed to by the shadow address register and |
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increments by two. |
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REPORT_STATUS |
14H |
— |
Loads a value into the DATA register. This value indicates |
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the status of your program: |
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Value |
Status |
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00 |
data latched |
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01 |
trapped |
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02 |
running |
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— indicates the RISM command is not available
17.8 EXECUTING PROGRAMS FROM REGISTER RAM
For those wanting to execute user programs from register RAM while in either serial port mode or SDU RISM execution, the RISM allows you to initialize the user program counter (UPC and UPC2), user processor status word (UPSW), and user window selection register (UWSR). Table 17-8 lists the registers and the register RAM addresses to which you may write new values.
Table 17-8. User Program Register and Register RAM Location
User Program Register |
Register RAM Address |
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Shadow Address |
5CH |
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UPC |
60H |
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UPC2 |
62H |
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UPSW |
64H |
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UWSR |
66H |
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Before attempting to execute a program from RAM, write the beginning address of the program to UPC and UPC2 at the addresses shown in Table 17-8. You need not change the UWSR and UPSW unless other flags need to be set for the program you are executing. After writing the UPC and UPC2 values, issue the GO command, which automatically initializes the UPC and begins code execution (refer to “SDU RISM Execution Go Command Example” on page 17-20). When
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