Port P7 (P77 To P70) - Philips CEM2100/00 Service Manual

5. I/O Ports

5.8 Port P7 (P77 to P70)

5.8 Port P7 (P77 to P70)
Port P7 is an 8-bit input/output port which can be configured as an input or output in one-bit unit.
Port P7 is also used as an analog input.
Input/output mode is specified by the P7 control register (P7CR1) and P7 input control register (P7CR2).
During reset, the P7CR1 is initialized to "0" the P7CR2 is initialized to "1" and port P7 becomes an input mode.
And the P7DR is initialized to "0".
When used as an output port, the corresponding bit of P7CR1 should be set to "1".
When used as an input port, the corresponding bit of P7CR1 should be set to "0" and then, the corresponding bit of
P7CR2 should be set to "1".
When used as an analog input, the corresponding bit of P7CR1 should be set to "0" and then, the corresponding bit
of P7CR2 should be set to "0".
When P7CR1 is "1", the content of the corresponding output latch is read by reading P7DR.
Note: Asterisk (*) indicates "1" or "0" either of which can be selected.
Table 5-6 Register Programming for Multi-function Ports
Function
Port input
Analog input
Port "0" output
Port "1" output
Table 5-7 Values Read from P7DR and Register Programming
Conditions
P7CR1 P7CR2
"0" "0"
"0" "1"
"0"
"1"
"1"
Programmed Value
P7DR P7CR1
* "0"
* "0"
"0" "1"
"1" "1"
Values Read from P7DR
"0"
Terminal input data
Output latch contents
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T5CL8
P7CR2
"1"
"0"
*
*