Datasheet

56F807 Technical Data Technical Data, Rev. 16
12 Freescale Semiconductor
2.5 Interrupt and Program Control Signals
Table 2-7 Data Bus Signals
No. of
Pins
Signal
Name
Signal
Type
State During
Reset
Signal Description
16 D0–D15 Input/O
utput
Tri-stated Data Bus— D0–D15 specify the data for external program or data
memory accesses. D0–D15 are tri-stated when the external bus is
inactive. Internal pullups may be active.
Table 2-8 Bus Control Signals
No. of
Pins
Signal
Name
Signal
Type
State During
Reset
Signal Description
1 PS
Output Tri-stated Program Memory Select—PS is asserted low for external program
memory access.
1 DS
Output Tri-stated Data Memory Select—DS is asserted low for external data memory
access.
1 WR
Output Tri-stated Write Enable—WR is asserted during external memory write cycles.
When WR is asserted low, pins D0–D15 become outputs and the device
puts data on the bus. When WR is deasserted high, the external data is
latched inside the external device. When WR
is asserted, it qualifies the
A0–A15, PS, and DS pins. WR can be connected directly to the WE pin of
a Static RAM.
1 RD
Output Tri-stated Read Enable—RD is asserted during external memory read cycles. When
RD is asserted low, pins D0–D15 become inputs and an external device is
enabled onto the device’s data bus. When RD is deasserted high, the
external data is latched inside the device. When RD
is asserted, it qualifies
the A0–A15, PS, and DS pins. RD can be connected directly to the OE pin
of a Static RAM or ROM.
Table 2-9 Interrupt and Program Control Signals
No. of
Pins
Signal
Name
Signal
Type
State During
Reset
Signal Description
1 IRQA
Input
(Schmitt)
Input External Interrupt Request A—The IRQA input is a synchronized
external interrupt request that indicates that an external device is
requesting service. It can be programmed to be level-sensitive or
negative-edge-triggered.
1 IRQB
Input
(Schmitt)
Input External Interrupt Request B—The IRQB input is an external
interrupt request that indicates that an external device is requesting
service. It can be programmed to be level-sensitive or
negative-edge-triggered.