7

Output Port Mode 1 - Typical Operation

General Operation

CDP1852 as an output port. The output drivers are always

on in this mode, so any data in the 8-bit register will be

present at the data-out lines when the CDP1852 is selected.

The N line and MRD connections between the CDP1852

and CDP1802 remain the same as in the input mode

configuration, but now the clock input of the CDP1852 is tied

to the TPB output of the CDP1802 and the SR output of the

CDP1852 will be used to signal the peripheral device that

valid data is present on its input lines. The microprocessor

issues an output instruction, and data from the memory is

strobed into the CDP1852 with the TPB pulse. When the

CDP1852 is deselected, the SR output goes high to signal

the peripheral device.

Detailed Operation (See Figure 7)

high and the MRD line goes low. The memory is accessed

M(R(X))

→ BUS and places data on the DATA BUS. This

data are strobed into the 8-bit register of the CDP1852 when

TPB goes high and latched on the TPB’s trailing edge. The

valid data thus appears on the CDP1852 output lines. When

line goes low and the SR output goes high. SR will remain

high until the trailing edge of the next TPB pulse, when it will

return low.

Dynamic Electrical Specifications

and 1 TTL Load

PARAMETER

(V)

LIMITS

UNITS

MIN

(NOTE 1)

TYP

MAX

MODE 1- OUTPUT PORT (See Figure 6)

Minimum Clock Pulse Width

5

-

130

260

ns

10

-

65

130

ns

Minimum Write Pulse Width

5

-

130

260

ns

10

-

65

130

ns

Minimum Clear Pulse Width

5

-

60

120

ns

10

-

30

60

ns

Minimum Data Setup Time

5-

-10

0

ns

10

-

-5

0

ns

Minimum Data Hold Time

5

-

75

150

ns

10

-

35

75

ns

Minimum Select-After-Clock Hold Time

5-

-10

0

ns

10

-

-5

0

ns

Clear to Data Out

5

-

140

280

ns

10

-

70

140

ns

Write to Data Out

5

-

220

440

ns

10

-

110

220

ns

Data In to Data Out

5

-

100

200

ns

10

-

50

100

ns

Clear to SR

5

-

120

240

ns

10

-

60

120

ns

Clock to SR

5

-

120

240

ns

10

-

60

120

ns

Select to SR

5

-

120

240

ns

10

-

60

120

ns

NOTE:

CDP1852, CDP1852C