User guide

Table 9–16 Interval Timing Control Register
Field Name Type Description
<7:6> Specifies which timer is to be configured by this
control byte. When set to ‘‘11’’, the control byte
is a status read command, not a Timer Control
operation.
As a status read command, the control byte can
be used to freeze the state of the timers for read-
back. Information pertaining to the assertion
state of the output pin, the mode of operation,
the read-write access mode, and so forth, is then
available by reading the timer data register.
<5:4> Sets the data interface to accept one or both of
the bytes of the timer’s 16-bit counter whenever
a read or a write operation to that timer occurs.
When set, all operations to the timer register
are in the format set until a new mode is set by
another control byte to the timer, according to
the following values:
Value Description
00 Latch count for read-back
01 LSB-only access mode
10 MSB-only access mode
11 LSB,MSB access mode
<3:1> Defines the operational mode of the timer,
according to the following values:
Value Description
011 Continuous
000 Single shot
<0> Sets the timer’s 16-bit counter to either binary
or BCD. When clear, the format is binary. When
set, the format is BCD.
Figure 9–14 shows a conceptual view of the operation of the timer bytewide data
interface. The ‘‘signal done’’ action is important where the completion of a data
access becomes an implicit start/go command to the timer.
Nbus 9–27