577
Chapter 16
Port Functions
Preliminary User’s Manual U15839EE1V0UM00
16.3.11 Port
CS
Port CS is a 3-bit input/output port in which input or output can be specified in 1-bit units. After reset,
port PCS0 operates as a chip select output pin (CS0). The port pins PCS3 and PCS4 operate as port
input after reset. Each port bit can be independently configured to port input, port output or peripheral
function
Note 1
.
This register can be read in 1-bit and 8-bit units.
Figure 16-32:
Port CS (PCS)
Remark:
In Input Mode: When the PCS register is read, the pin levels at that time are read. Writing
to the PCS register writes the values to that register. This does not affect
the input pins.
In Output Mode:When the PCS register is read, the values of PCS are read. Writing to the
PCS register writes the values to that register and those values are
immediately output.
Besides functioning as a port, in control mode, it also can operate as the chip select signal output when
memory is accesses externally.
Notes: 1. If using peripheral functions, the direction setting for the respective port bit is not forced
automatically. Port bit direction has to be programmed according to the peripheral function
requirement by setting the port mode register.
2. The reset value of register PCS is 00H. Due to the input mode of the port after reset, the
read input value is determined by the port pins.
(1)
Operation in control mode
Caution:
In case that a port pin CS0, CS3 or CS4 operates as a chip select output port, it is rec-
ommended to plug in an external pull up resistor to that pin.
7
6
5
4
3
2
1
0
Address
At Reset
PCS
0
0
0
PCS4
PCS3
0
0
PCS0
FFFFF008H 00H
Note 2
Bit Position
Bit Name
Function
4, 3, 0
PCSn
(n = 4, 3, 0)
Input/output port
Port
Alternate Pin Name
Remarks
Block Type
Port AH
PCS4
CS0
Chip select signal output
C
PCS3
CS3
Chip select signal output
PCS0
CS4
Chip select signal output
Summary of Contents for mPD703128
Page 6: ...6 Preliminary User s Manual U15839EE1V0UM00 ...
Page 20: ...20 Preliminary User s Manual U15839EE1V0UM00 ...
Page 32: ...32 Preliminary User s Manual U15839EE1V0UM00 MEMO ...
Page 154: ...154 Preliminary User s Manual U15839EE1V0UM00 MEMO ...
Page 238: ...238 Preliminary User s Manual U15839EE1V0UM00 MEMO ...
Page 356: ...356 Preliminary User s Manual U15839EE1V0UM00 MEMO ...
Page 522: ...522 Preliminary User s Manual U15839EE1V0UM00 MEMO ...
Page 600: ...600 Preliminary User s Manual U15839EE1V0UM00 MEMO ...
Page 610: ...610 Preliminary User s Manual U15839EE1V0UM00 ...
Page 612: ......