C161RI_1 Datasheet, PDF (121/317 Pages) Siemens Semiconductor Group – 16-Bit CMOS Single-Chip Microcontroller

Parallel Ports
C161RI
Pin P3.12 (BHE/WRH) is one more pin with an alternate output function. However, its structure is
slightly different (see figure below), because after reset the BHE or WRH function must be used
depending on the system startup configuration. In these cases there is no possibility to program any
port latches before. Thus the appropriate alternate function is selected automatically. If BHE/WRH
is not used in the system, this pin can be used for general purpose IO by disabling the alternate
function (BYTDIS = ‘1’ / WRCFG = ‘0’).
Write DP3.x
Direction
Latch
Ι
Read DP3.x
n
t
e
r
n
Write P3.x
a
l
Port Output
B
Latch
u
s
Read P3.x
x = 15, 12
’1’
1
MUX
0
Alternate
Function
Enable
Alternate
Data
Output
1
MUX
0
1
MUX
0
Output
Buffer
P3.12/BHE
P3.15/CLKOUT
Clock
Input
Latch
MCB02073
Figure 7-12
Block Diagram of Pins P3.15 (CLKOUT) and P3.12 (BHE/WRH)
Note: Enabling the BHE or WRH function automatically enables the P3.12 output driver. Setting bit
DP3.12 = ‘1’ is not required.
Enabling the CLKOUT function automatically enables the P3.15 output driver. Setting bit
DP3.15 = ‘1’ is not required.
Semiconductor Group
7-19
1998-05-01