em78p257 ELAN Microelectronics Corp, em78p257 Datasheet - Page 14

• Manufacturer Part Number: em78p257
• Description: 8-bit Microcontroller
• Manufacturer: ELAN Microelectronics Corp

This specification is subject to change without prior notice.
5. R4 (RAM Select Register)
6. R5 ~ R6 (Port 5 ~ Port 6)
7. R7 (Port 7 )
• Bit6 (IOCS) Select the Segment of the control register.
• Bit5 (PS0) Page select bits. PS0 is used to select a program memory page. When executing a "JMP",
• Bit 4 (T) Time-out bit.
• Bit 3 (P) Power down bit.
• Bit 2 (Z) Zero flag.
• Bit 1 (DC) Auxiliary carry flag.
•The Bit7 set to “0” as all time.
• Bit 6 is used to select bank 0 or bank 1.
• Bits 5~0 are used to select a register (address: 00~0F, 10~3F) in the indirect addressing mode.
• See the configuration of the data memory in Fig. 5.
• R5 and R6 are I/O registers.
• Only the lower 6 bits of R5 are available.(applicable to EM78P257A)
• The upper 2 bits of R5 are fixed to 0. (if EM78P257A is selected)
• R7 is I/O registers.
• Only the lower 2 bits of R7 are available.
• Bit 0 (C) Carry flag.
"CALL", or other instructions that causes the program counter to change (e.g. MOV R2,A), PS0 is
loaded into the 11th bit of the program counter, selecting one of the available program memory
pages. Note that RET (RETL, RETI) instruction does not change the PS0 bits. That is, the return will
always be back to the page from where the subroutine was called, regardless of the current PS0 bit
setting.
Set to 1 with the "SLEP" and "WDTC" command, or during power on and reset to 0 by WDT time-out.
Set to 1 during power on or by a "WDTC" command and reset to 0 by a "SLEP" command.
Set to "1" if the result of an arithmetic or logic operation is zero.
0 = Segment 0( IOC50~IOCF0 ) selected;
1 = Segment 1( IOC51~IOCC1 ) selected;
PS0
7
-
0
1
6
-
Program memory page [Address]
Page 0 [000-3FF]
Page 1 [400-7FF]
5
-
4
-
14
3
-
2
-
I/O
1
EM78P257
07.27.2004 (V1.4)
OTP ROM
I/O
0