SEGA SATURN DEVELOPER'S MANUAL

Program end interrupt flag (8 [bit 18] in Figure 3.14)
E (R) End flag: When the end of the program is detected by the ENDI instruction, this flag is set to 1 and a program end interrupt is generated. This flag is reset by reading.
Step execution control bit (9 [bit 17] in Figure 3.14)
ES (W) Execute Step control bit: Writing 1 while the program is stopped (when the program execution control flag is 0) executes the program one step. Invalid during execution.
Program execution control flag (10 [bit 16] in Figure 3.14)
EX (R / W) program EXecute control flag: Controls program execution. When 1 is written, execution starts, and when 0 is written, execution stops. When this flag is read, it can be judged whether it is running (1) or stopped (0).
Program counter transfer enable bit (11 [bit 15] in Figure 3.14)
LE (W) Load Enable bit: This bit determines whether to load the program RAM address (see below) into the program counter. When 1 is written to this bit, the program RAM address at that time is loaded into the program counter. Loading is not possible during program execution (when the program execution control flag is 1).
Program RAM address (12-19 [bit 7-0] in Figure 3.14)
P7-0 (R / W) Program RAM address bit7-0: Stores the program RAM address. The start address can be set and the stop address can be read.