Texas Instruments MSC1210 manual 1 I/O Ports P0, P1, P2, and P3, AD7

MSC1210 Pin-Out

Table 1−1 Pin Descriptions of the MSC1210 (Continued)

Pin #	Name	Description
46, 47,	P0.0−P0.7	P0.5	AD5	Address/Data Bit 5
49-54
		P0.6	AD6	Address/Data Bit 6
		P0.7	AD7	Address/Data Bit 7
55, 56,	P1.0−P1.7	Port 1 is a bidirectional I/O port. The alternate functions for Port 1 are
59−64		listed below.
		Port 1—Alternate Functions:
		PORT	ALTERNATE	MODE
		P1.0	T2	T2 Input
		P1.1	T2EX	T2 External Input
		P1.2	RxD1	Serial Port Input
		P1.3	TxD1	Serial Port Output
		P1.4		External Interrupt/Slave Select
			INT2/SS
		P1.5		External Interrupt/Master Out−Slave In
			INT3/MOSI
		P1.6	INT4/MISO	External Interrupt/Master In−Slave Out
		P1.7		External Interrupt/Serial Clock
			INT5/SCK

1.2.1I/O Ports (P0, P1, P2, and P3)

Of the 64 pins on the MSC1210, 32 of them are dedicated to I/O lines that have a one-to-one relation with SFRs P0, P1, P2, and P3. The developer may raise and lower these lines by writing 1s or 0s to the corresponding bits in the SFRs. Likewise, the current state of these lines may be found by reading the corre- sponding bits of the SFRs.

All of the ports have optional pull-up resistors that are enabled when the port is in 8051 mode, as configured by the PxDDRL/H SFRs. The pull-up resistors are disabled when the port is configured in any other mode, or when accessing external memory.

1.2.1.1Port 0

Port 0 is dual-function: in some designs port 0 I/O lines are available to the de- veloper to access external devices, while in other designs it is used to access external memory. If the circuit requires external RAM, the microcontroller will use port 0 to latch in/out the 8-bit data word, as well as the low eight bits of the address in response to a MOVX instruction, as long as the hardware configu- ration registers are set up correctly. Port 0 I/O lines may be used for other func- tions as long as external data memory is not being accessed at the same time and the hardware configuration registers are set up correctly. If the circuit re- quires external code memory, the microcontroller will use port 0 I/O lines to ac- cess each instruction to be executed. In this case, port 0 cannot be used for other purposes, because the state of the I/O lines are constantly being modi- fied to access external code memory.

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