Slow AMBA Peripherals
13-24
GMS30C7201 Data Sheet
13.4.2 Hardware interface and signal description
The Keyboard Interface Controller is connected to the APB bus.
13.4.3 Keyboard interface controller unit introduction
The interface controller is designed to communicate with the external keyboard. The
keyboard interface uses the pins
scanin
,
scanout
and all of the APB signal. It is
possible to select one of four scan clock modes.
Name
Type
Source/
Destination
Description
PCLK
In
UART Clock
UART Clock. The input frequency from UART is
3.6864MHz.
PCLK
is used to generate the scan
clock.
RESET
In
APB Bridge
Active LOW reset signal.
PA
In
APB Bridge
This is the peripheral address bus, which is used by
an individual peripheral for decoding register
accesses to that peripheral.
The addresses become valid before
PSTB
goes
HIGH, and remain valid after
PSTB
goes LOW.
PD[31:0]
InOut
APB Bridge/
Keyboard Interface
This is the bi-directional peripheral data bus. The
data bus is driven by this block during read cycles
(when
PWRITE
is LOW).
PSTB
In
APB Bridge
This strobe signal is used to time all accesses on
the peripheral bus. The falling edge of
PSTB
is
coincident with the falling edge of
BCLK
.
PWRITE
In
APB Bridge
When HIGH, this signal indicates a write to a
peripheral; when LOW, it indicates a read from a
peripheral.
This signal has the same timing as the peripheral
address bus. It becomes valid before
PSTB
goes
HIGH and remains valid after
PSTB
goes LOW.
PSEL
In
APB Bridge
When HIGH, this signal indicates that this module
has been selected by the APB bridge. This
selection is a decode of the system address bus
(ASB). For more details, see
AMBA Peripheral Bus
Controller
(ARM DDI 0044).
Scanout
Out
Keypad
This assigns the x-axis' scan line. The value is
changed periodically so as to cover every key
matrix. During one keyboard scan,
scanout
can
have 11 different values. Active LOW signal.
Scanin
In
Keypad
This indicates which key is pressed in the assigned
scan line. Active LOW signal.
INTKBD
Out
Interrupt Controller
Interrupt signal to the Interrupt Controller module.
This signal indicates if 11th column key scan is
finished. Active HIGH signal.
Table 13-15: Signal descriptions