Master Control Registers
VL-486-4 Reference Manual
CIO Chip – 77
Table 53: Master Configuration Control Register (Continued)
Bit
Mnemonic
Description
D4
PCECT3E
Port C and Counter/Timer 3 Enable — This bit enables both Port C and
Counter/Timer 3.
PCECT3E = 0
Counter/Timer 3 is put into an initialized state: its IP cannot
be set (however, if IP was already set, clearing CT1E does
not clear IP), the Count In Progress (CIP) flag is cleared,
Read Counter Control (RCC) is forced to 0, and all trigger
inputs are ignored. Handshake logic for Ports A and B is
forced into an idle state and the internal Acknowledge Input
(ACKIN) signal is forced High. This allows the start-up of
handshake operations to be precisely controlled.
Inhibits Port C logic from issuing an interrupt request (its IP
cannot be set); however, if IP was already set, clearing PBE
inhibits READY/WAIT assertion, holds all1's catchers in a
transparent condition, and forces the Port C I/O lines into a
high-impedance state.
PCECT3E = 1
Counter/timer 3 and Port C function normally.
D3
PLC
Port Link Control — Unsupported.
PLC = 0
Ports A and B operate as two independent 8-bit ports.
PLC = 1
Unsupported
D2
PAE
Port A Enable — This bit allows Port A to be configured initially without
setting its IP erroneously or having its I/O lines go low-impedance until it is
safe to do so.
PAE = 0
Inhibits the Port A logic from issuing an interrupt request (its
IP cannot be set); however, if IP was already set, clearing
PBE inhibits READY/WAIT assertion, holds all 1's catchers
in a transparent condition, and forces the Port A I/O lines
into a high-impedance state.
PAE = 1
Allows Port A to operate normally
D1-D0
LC1-LC0
Counter/Timer Link Controls — These two bits specify if and how
Counter/Timers 1 and 2 are linked. The Counter/Timers must be linked before
they are enabled.
LC1
LC0
Mode
0
0
Counter/Timers are independent
0
1
Counter/Timer 1's output (inverted) gates
Counter/Timer 2
1
0
Counter/Timer 1's output (inverted) triggers
Counter/Timer 2
1
1
Counter/Timer 1's output (inverted) is
Counter/Timer 2's count input