Intel 8XC196NT, User Manual

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8XC196NT USER’S MANUAL
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15.10.3 Executing Programs from Internal RAM
For those wanting to execute user programs from internal RAM while in serial port programming
mode, the RISM allows you to initialize the user program counter (PC), window selection register
(WSR), and processor status word (PSW). Table 15-13 lists the registers, the default assumed by
the RISM, and the test ROM address to which you may write new values.
Before attempting to execute a program from internal RAM or OTPROM, write the beginning
address of the program to the PC at the test ROM address shown in Table 15-13. You need not
change the WSR and PSW unless other flags need to be set for the program you are executing.
After writing the PC value, issue the GO command, which automatically initializes the PC and
begins code execution. When the RISM interrupts or halts the program, it writes the user PC,
WSR (which includes INT_MASK1), and PSW (which includes INT_MASK) to the test ROM
locations.
Internal RAM locations 4EH–63H are used as registers for serial port programming mode. Pro-
grams executing from internal RAM should not alter these locations.
15.10.4 Reduced Instruction Set Monitor (RISM)
When you enter serial port programming mode, the device begins executing its RISM program.
The RISM is executed in 16-bit mode, so addresses are limited to 64 Kbytes and the PC is limited
to 16 bits. You communicate with the device by sending RISM commands from any smart termi-
nal across the TXD and RXD pins at a fixed baud rate.
Upon entering serial port programming mode, the device enters a waiting loop, called
Monitor_Pause, in which it waits for RISM commands to arrive across the serial port. The com-
mands are each one byte in length and have values between 00H and 1FH. A value between 00H
and 1FH is considered a command unless it follows a data latch enable (SET_DLE_FLAG) com-
mand. The SET_DLE_FLAG command sets the DLE flag in the MODE register (57H). The DLE
flag alerts the RISM to store the next byte in the DATA register, a 32-bit first-in-last-out (FILO)
register located at 58H.
Table 15-13. User Program Register Values and Test ROM Locations
User Program Register RISM Default Test ROM Address
PC 2080H 5EH
WSR 1000H 60H
PSW 0200H 62H