CMX850L8 View Datasheet(PDF) - CML Microsystems Plc
Part Name
Description
MFG CO.
'CMX850L8' PDF : 103 Pages View PDF
Communications Controller
CMX850
KBSTAT Register b2: Overflow status (read-only)
This bit is set to a 1 if the 8-character keyboard data buffer KBBUF overflows, indicating that data
has been lost. This register bit will then remain at logic 1 until it is cleared either by writing 1 to the
overflow clear bit (KBSTAT bit 3) or by disabling the keyboard encoder using KBCON bit 7.
KBSTAT Register b1: Sleep indicator (read-only)
This bit is set to a 1 if the keyboard encoder is enabled but has entered sleep mode (this requires
KBCON bit 6 to be set), otherwise the sleep indicator bit will be 0.
KBSTAT Register b0: Empty flag (read-only)
This bit will set to a 0 when the keyboard data buffer KBBUF contains information, indicating that
one or more key presses or key releases have been detected, and is set to a 1 after all data has
been read from KBBUF. This bit is connected to the 8051 µC’s Int4 input, allowing the keyboard
encoder to be interrupt driven. In this case, Int4 should be configured as a level interrupt rather than
edge triggered.
1.5.10.3
Keyboard Buffer Register (KBBUF)
KBBUF: Read-only. SFR Address $EE
This read-only register contains information about the location of any key press or release that the keyboard
encoder has detected. The keyboard encoder can buffer up to 8 characters; the data is retrieved by
repeatedly reading the KBBUF register.
Bit:
7
6
5
4
Press /
release
Row Address
3
2
1
0
Column address
KBBUF Register b7: Key press/release indication
b7 = 1 Key press detected
b7 = 0 Key release detected
KBBUF Register b6-4: Row address
These bits indicate on which keyboard row a key press or release was detected
(000 = row 0, 001 = row 1, etc).
KBBUF Register b3-0: Column address
These bits indicate on which keyboard column a key press or release was detected
(0000 = column 0, 0001 = column 1, etc).
© 2003 CML Microsystems Plc
46
D/850/6
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