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5-1
CHAPTER 5
I/O PORTS
5.1 PORT 0 AND EPORT
The I/O ports of the 87C196CB are functionally identically to those of the 8XC196NT. However,
the 87C196CB implements all eight pins of port 0, and the 100-pin 87C196CB also implements
all eight pins of the EPORT. The associated registers have been modified to include bits corre-
sponding to the upper nibble of the ports. Table 5-1 provides an overview of the 8XC196CB’s
I/O ports. Figure 5-1 illustrates the port 0 pin state register, and Figures 5-2 through 5-5 illustrate
the EPORT registers.
Table 5-1. 87C196CB Input/Output Ports
Port Bits Type Direction Associated Peripheral(s)
Port 0 8 Standard Input-only A/D converter
Port 1 8 Standard Bidirectional EPA and timers
Port 2 8 Standard Bidirectional SIO, interrupts, bus control, clock gen.
Port 3 8 Memory-mapped Bidirectional Address/data bus
Port 4 8 Memory-mapped Bidirectional Address/data bus
Port 5 8 Memory-mapped Bidirectional Bus control, slave port
Port 6 8 Standard Bidirectional EPA, SSIO
EPORT
4 (84-pin CB)
8 (100-pin CB)
Memory mapped Bidirectional Extended address lines
P0_PIN
Address:
Reset State:
1FDAH
XXH
Each bit of the port 0 pin input (P0_PIN) register reflects the current state of the corresponding pin,
regardless of the pin configuration.
7 0
PIN7 PIN6 PIN5 PIN4 PIN3 PIN2 PIN1 PIN0
Bit
Number
Bit
Mnemonic
Function
7:0 PIN7:0 Port 0 Pin
x
Input Value
This bit contains the current state of P0.
x
.
Figure 5-1. Port
x
Pin Input (P
x
_PIN) Register