CD1865
—
Intelligent Eight-Channel Communications Controller
120
Datasheet
Bit 5 indicates whether the CD1865 is looking for a Start bit. If bit 5 is a
‘
1
’
, it is looking. If bit 5 is
a
‘
0
’
, it is receiving a character.
9.4.8
Receive Time-Out Period Register
This register defines the time period for two functions related to the Receive FIFO. As each
character is moved to the Receive FIFO, the Receive Timer is reloaded with the Receive Data
Time-out Period. The Receive Timer is then decremental on each tick of the Prescaler Counter. If
the Receive Timer reaches a
‘
0
’
, it causes a Receive Good Data Service Request.
There is another optional feature called No New Data Time-out. When enabled, the Receive Timer
generates a Receive Exception if the timer expires after the last data is transferred from the FIFO to
the host. This is intended to tell the host that no more data is arriving, and to go ahead and process
the buffer.
The Receive Time-out Period register defines the time-out period for both of these functions. It
counts in time increments defined by the prescaler.
9.4.9
Receive Bit Rate Period Registers (High/Low)
Register Name: RTPR
Register Description: Receive Time-Out Period Register
Default Value: 5
Access: Read/Write
Bit 7
Bit 6
8-Bit Hex Address: $18
Intel Hex Address: $30
Motorola Hex Address: $31
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
Receiver Data Time-out Period
Register Name: RBPRH
Register Description: Receive Bit Rate Period Register (High)
Default Value: 0
Access: Read/Write
Bit 7
Bit 6
8-Bit Hex Address: $31
Intel Hex Address: $62
Motorola Hex Address: $63
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
Receiver Bit Rate Divisor Byte
Register Name: RBPRL
Register Description: Receive Bit Rate Period Register (Low)
Default Value: 0
Access: Read/Write
Bit 7
Bit 6
8-Bit Hex Address: $32
Intel Hex Address: $64
Motorola Hex Address: $65
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
Receiver Bit Rate Divisor Byte