IA88C00
Data Sheet
Microcontroller
As of Production Version -01
I/O Ports
The IA88C00 contains 40 I/O lines arranged into five 8-bit ports. Each line is TTL-compatible and can be
configured as a address/data line. Each port includes an input register, an output register and a register
address. The input register stores data coming into the port. The output register stores data to be written to
a port. Reading a port’s register address returns the value in the input register. Writing a port’s register
address loads the value in the output register. If the port is configured for an output, this value will appear
on the external pins.
When the CPU reads the bits configured as outputs, the data on the external pins is returned. Under
normal output loading, this has the same effect as reading the output register, unless the bits are
configured as open-drain outputs.
The ports can be configured as shown in Figure 59.
Figure 59. Port Configuration
Port
0
Configuration Choices
High address and/or 0
1
Multiplexed Low address/data or data only
Control I/O for UART, handshake channels, counter/timers,
general I/O and external interrupts
Low address or general I/O
2 & 3
4
Port 0
Port 0 can be assigned on a bit-by-bit basis as either general I/O or as address bits for external memory.
The bits configured as I/O can be either all inputs or all outputs, they cannot be mixed. If configured for
outputs, they can be either push-pull or open-drain types. I/O direction is controlled by mode control
register R241. Push-pull or open-drain selection is controlled by mode control register R241.
Port 0 can be placed under handshake control handshake channel 1.
Any bits configured as I/O can be accessed via R208.
Port 0 bits configured as address outputs cannot be accessed via the register, and initially the four lower
bits are configured as addresses eight through twelve.
Port 1
Port 1 is bi-directional. Port 1 is configured as either a byte wide Mux'ed Address(low byte)/Data bus or
as Data bus only. This control is via the demux pin. The port address for Port 1 is R209. Port 1 drive
characteristics can be selected to be either Push/Pull or Open Drain. This control is via the mode/control
register R241 Bank0, ControlRegR241B0
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