W78E516B
Port 4 (D8H)
BIT
7
6
5
4
3
2
1
0
NAME
-
-
-
-
P43
P42
P41
P40
Reserve
Reserve
Reserve
Reserve
Port 4 Data bit which outputs to pin P4.3.
Port 4 Data bit. which outputs to pin P4.2.
Port 4 Data bit. which outputs to pin P4.1.
Port 4 Data bit which outputs to pin P4.0.
FUNCTION
In-System Programming (ISP) Mode
The W78E516B equips one 64K byte of main MTP-ROM bank for application program (called
APROM) and one 4K byte of auxiliary MTP-ROM bank for loader program (called LDROM). In the
normal operation, the microcontroller executes the code in the APROM. If the content of APROM
needs to be modified, the W78E516B allows user to activate the In-System Programming (ISP) mode
by setting the CHPCON register.
The CHPCON is read-only by default, software must write two
specific values 87H, then 59H sequentially to the CHPENR register to enable the CHPCON
write attribute. Writing CHPENR register with the values except 87H and 59H will close
CHPCON register write attribute.
The W78E516B achieves all in-system programming operations
including enter/exit ISP Mode, program, erase, read ... etc, during device in the idle mode. Setting the
bit CHPCON.0 the device will enter in-system programming mode after a wake-up from idle mode.
Because device needs proper time to complete the ISP operations before awaken from idle mode,
software may use timer interrupt to control the duration for device wake-up from idle mode. To
perform ISP operation for revising contents of APROM, software located at APROM setting the
CHPCON register then enter idle mode, after awaken from idle mode the device executes the
corresponding interrupt service routine in LDROM. Because the device will clear the program counter
while switching from APROM to LDROM, the first execution of RETI instruction in interrupt service
routine will jump to 00H at LDROM area. The device offers a software reset for switching back to
APROM while the content of APROM has been updated completely.
Setting CHPCON register bit 0,
1 and 7 to logic-1 will result a software reset to reset the CPU.
The software reset serves as a
external reset. This in-system programming feature makes the job easy and efficient in which the
application needs to update firmware frequently. In some applications, the in-system programming
feature make it possible to easily update the system firmware without opening the chassis.
SFRAH, SFRAL:
The objective address of on-chip MTP-ROM in the in-system programming mode.
SFRFAH contains the high-order byte of address, SFRFAL contains the low-order
byte of address.
SFRFD:
The programming data for on-chip MTP-ROM in programming mode.
SFRCN:
The control byte of on-chip MTP-ROM programming mode.
-7-
Publication Release Date: February 2000
Revision A3
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