17.6.1.2SDU RISM Data Transfer After

Table 17-6 shows the code RAM contents after each command has been executed.

Table 17-6. After RISM Command Execution

RISM Command	400H	401H	402H	403H	404H	405H

RISM_IDLE	80H	U	U	U	U	U

READ_BYTE	81H	U	U	DATA(L)	U	U

READ_WORD	82H	U	DATA(L)	DATA(H)	U	U

WRITE_BYTE	83H	U	U	U	U	U

WRITE_WORD	84H	U	U	U	U	U

GO	85H	U	U	U	U	U

HALT	86H	U	U	U	U	U

READ_NEXT_BYTE	81H	U	U	DATA(L)	U	U

READ_NEXT_WORD	82H	U	DATA(L)	DATA(H)	U	U

WRITE_NEXT_BYTE	83H	U	U	U	U	U

WRITE_NEXT_WORD	84H	U	U	U	U	U

U = unchanged

NOTE

For the read byte commands, the data is returned in location 403H (not 402H). This is because the SDU cannot correctly perform a byte read on an even address. All reads from the code RAM are 16-bit transfers, and there is no logic to move the low byte to the high byte as would be required to correctly read an even byte.

In the command byte column of Table 17-6, notice that the RISM has set the most-significant bit of the command byte to signal to the monitor software that it has completed executing a command byte. This allows the host software to determine when the RISM is done processing one command so that it can accept another command.

17.6.2 SDU RISM Execution Circuit

Figure 17-5 shows the recommended circuit for accessing the SDU RISM execution routine.

To standardize the connector interface to the SDU port, we recommend that you use a 10-pin, 2- row I/O expansion connector. This low cost, readily available standard connector can be easily added to any printed-circuit board (PCB) after manufacturing of the module.

To prevent mis-socketing and ensure proper cable connection, we recommend that you remove the square pin at position #1 (Key) and block the adjoining cable position.

17-13