Mitsubishi DS907x SIP manual Parallel Program Load Mode, 8751±COMPATIBLE Program Load Cycles ±3

USER'S GUIDE

PARALLEL PROGRAM LOAD MODE

Table 16±3 summarizes the selection of the available Parallel Program Load cycles. Figure 16±4 illustrates the timing associated with these cycles.

8751±COMPATIBLE PROGRAM LOAD CYCLES Table 16±3

MODE	RST	PSEN		PROG	EA	P2.7	P2.6	P2.5
Program	1	0	0		VPP	1	0	X
Security Set	1	0	0		VPP	1	1	X
Verify	1	X		X	1	0	0	X
Prog Expanded	1	0	0		VPP	0	1	0
Verify Expanded	1	0	1		1	0	1	0
Prog MCON or Key	1	0	0		VPP	0	1	1
Verify MCON	1	0	1		1	0	1	1

The Program cycle is used to load a byte of data into a register or memory location within the DS5000. The Verify cycle is used to read this byte back for compari- son with the originally loaded value to verify proper load- ing. The Security Set cycle may be used to enable the Software Security feature of the DS5000. One may also enter bytes for the MCON register or the Encryption Key using the Program MCON cycle. When using this cycle, the absolute register address must be presented at Port 1 and 2 as is the normal Program cycle (Port 2 should be 00H). The MCON contents can be likewise verified us- ing the Verify MCON cycle.

When the DS5000 first detects a Parallel Program Strobe pulse or a Security Set Strobe pulse while in the Program Load mode following a Power±On Reset, the internal hardware of the DS5000 is initialized so that an existing 4K byte 8751 program can be programmed into a DS5000 with little or no modification. This initialization automatically sets the Range Address for 8K bytes and maps the lower 4K byte bank of Embedded RAM as Pro- gram Memory. The top 4K bytes of Embedded RAM are mapped as Data Memory. In order to program code (and thereby use the DS5000±enhanced capability), the Pro- gram/Verify Expanded cycles can be used. Up to 32K bytes of program code can be entered and verified. Note that the expanded 32K byte Program/Verify cycles take much longer than the standard cycles.

A typical parallel loading session would follow this pro- cedure. First, set the contents of the MCON register with the correct range and partition (if using expanded pro- gramming). Next, the Encryption Key can be loaded if desired. Then, program the DS5000 using either stan- dard or expanded program cycles and verify. Last, turn on the security lock using a Security Set cycle.

The Security Set strobe pulse from an 8751±compatible programming system can be used to enable the Soft- ware Security feature of the DS5000. To explain this op- eration on the DS5000, it is useful to review how this function works with the 8751. The Security Set Strobe pulse is used to program the EPROM Security Lock bit on an 8751. The programmed bit disables the on±chip EPROM memory from being read back during a Verify cycle. The bit can only be erased by UV light when the rest of the program is erased.

With the DS5000, the Security Set Strobe pulse serves a similar function for its NV RAM±based Security Lock which when set disables the NV RAM from beginning read either through a Verify cycle in the Parallel Pro- gram mode or back through the serial port in the Serial Port mode. When a Security Set Strobe pulse is re- ceived by the DS5000, the current state of the Security Lock bit is checked. If it is currently a 0, it will be set to 1. The Security Lock can be cleared by clearing the LSB of the MCON register.

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