W78E58B Winbond, W78E58B Datasheet - Page 11

• Manufacturer Part Number: W78E58B
• Description: 8 BIT MICROCONTROLLER
• Manufacturer: Winbond

In-System Programming (ISP) Mode
The W78E58B equips one 32K byte of main ROM bank for application program (called APROM) and
one 4K byte of auxiliary 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
W78E58B 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 W78E58B 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.
REGISTER
P4xAL
P4xAH
ADDRESS BUS
WRITE
READ
P4 REGISTER
P4.x
P4xCMP0
P4xCMP1
REGISTER
EQUAL
Bit Length
Selectable
comparator
P4xCSINV
- 11 -
P4xFUN0
P4xFUN1
P4.x INPUT DATA BUS
Publication Release Date: March 18, 2002
DATA I/O
RD/WR_CS
WR_CS
RD_CS
MUX 4->1
W78E58B
P4.x
PIN
Revision A3