9.2 Parallel Port B

Parallel Port B, has eight pins that can programmed individually to be inputs and outputs.

After reset, Parallel Port B comes up as six inputs (PB[5:0]) and two outputs (PB7 and PB6). The output value on pins PB6 and PB7 (package pins 99, 100) will be low.

Table 9-3. Parallel Port B Registers

Register Name

Mnemonic

I/O address

R/W

Reset

 

 

 

 

 

Port B Data Register

PBDR

0x40

R/W

00xxxxxx

 

 

 

 

 

Port B Data Direction Register

PBDDR

0x47

W

11000000

 

 

 

 

 

Table 9-4. Parallel Port B Register Bit Functions

 

Bit 7

Bit 6

Bit 5

Bit 4

Bit 3

Bit 2

Bit 1

Bit 0

 

 

 

 

 

 

 

 

 

PBDR

 

 

 

 

 

 

 

 

(R/W)

PB7

PB6

PB5

PB4

PB3

PB2

PB1

PB0

adr = 0x040

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

PBDDR

dir =

dir =

dir =

dir =

dir =

dir =

dir =

dir =

(W)

out

out

out

out

out

out

out

out

adr = 0x047

 

 

 

 

 

 

 

 

 

When the auxiliary I/O bus is enabled, Parallel Port B bits 2:7 provide 6 address lines, the least significant 6 lines of the 16 lines that define the full I/O space.

When the slave port is enabled, parallel port lines PB2–PB7 are assigned to various slave port functions. However, it is still possible to read PB0–PB5 using the Port B data register even when lines PB2–PB7 are used for the slave port. It is also possible to read the signal driving PB6 and PB7 (this signal is on the signaling lines from the slave port logic).

Regardless of whether the slave port is enabled, PB0 reflects the input of the pin unless Serial Port B has its internal clock enabled, which causes this line to be driven by the serial port clock. PB1 reflects the input of the pin unless Serial Port A has its internal clock enabled.

PBDR—Parallel Port B data register. Read/Write.

PBDDR—Parallel Port B data direction register. A "1" makes the corresponding pin an output. This register is write only.

User’s Manual

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Jameco Electronics 3000, 2000 manual Parallel Port B Registers, Parallel Port B Register Bit Functions