W78C438C_06 Datasheet, PDF (11/22 Pages) Winbond – 8-BIT MICROCONTROLLER

W78C438C
5.4 Newly Added Special Function Registers
The W78C438C uses four newly defined special function registers, which are described in Table 4. To
read/write these registers, use the "MOV direct" or "read-modify-write" instructions.
REGISTER ADDR.
FUNCTION
LENGTH
1
HB
A1H
During the execution of "MOVX @Ri,"
the content of HB is output to AP6.
8
EPMA.7 determines functions of AP7.
2 EPMA A2H _{EPMA.3−EPMA.0 determine values of} 8
AP7<3:0> when EPMA.7 is "0."
R/W
TYPE
R/W
R/W
VALUE AFTER
RESET
00H
70H
3
P8
A6H The content of P8 is output to port 8.
8
The bits of XICON determine/show the
4 XICON C0H functions/status of INT2 − INT3 . Bit-
8
addressable.
R/W
R/W
0FFH
00H
Notes:
Table 4. Newly Added Special Function Registers of the W78C438C
1. The instructions used to access these nonstandard registers may cause assembling errors with respect to the 2500 A. D.
assembler, but these errors can be ignored by adding directive ".RAMCHK OFF" ahead these instructions.
2. In the newly added SFR of W78C438C, only XICON register is bit-addressable.
5.5 Power Reduction Function
The W78C438C supports power reduction just as the W78C32 does. The following table shows the
status of the external pins during the idle and power-down modes.
FUNCTION
ALE, PSEN
P0−P3, P8
DP4
Idle
11
Port Data
Floating
Power Down
00
Port Data
Floating
Note: AP7 is either 0 or a value decoded by AP6<7:6>, depending on the value of EPMA.7.
AP5, AP6
Address
Address
AP7
Note
Note
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Publication Release Date: December 4, 2006
Revision A6