W78C438C40FL Datasheet W78C438C40FL | P10-P12

W78C438C

- 10 -

5.4 Newly Added Special Function Registers

The W78C438C uses four newly defined special function registers, which are described in Table 4. To

read/write these registers, use the "MOV direct" or "read-modify-write" instructions.

REGISTER ADDR. FUNCTION LENGTH

R/W

TYPE

VALUE AFTER

RESET

1 HB A1H

During the execution of "MOVX @Ri,"

the content of HB is output to AP6.

8 R/W 00H

2 EPMA A2H

EPMA.7 determines functions of AP7.

EPMA.3−

EPMA.0 determine values of

AP7<3:0> when EPMA.7 is "0."

8 R/W 70H

3 P8 A6H The content of P8 is output to port 8. 8 R/W 0FFH

4 XICON C0H

The bits of XICON determine/show the

functions/status of

INT2

−

INT3

. Bit-

addressable.

8 R/W 00H

Table 4. Newly Added Special Function Registers of the W78C438C

Notes:

1. The instructions used to access these nonstandard registers may cause assembling errors with respect to the 2500 A. D.

assembler, but these errors can be ignored by adding directive ".RAMCHK OFF" ahead these instructions.

2. In the newly added SFR of W78C438C, only XICON register is bit-addressable.

5.5 Power Reduction Function

The W78C438C supports power reduction just as the W78C32 does. The following table shows the

status of the external pins during the idle and power-down modes.

FUNCTION

ALE,

PSEN

P0

−

P3, P8

DP4 AP5, AP6 AP7

Idle 1 1 Port Data Floating Address Note

Power Down 0 0 Port Data Floating Address Note

Note: AP7 is either 0 or a value decoded by AP6<7:6>, depending on the value of EPMA.7.

W78C438C

Publication Release Date: March 10, 2010

- 11 - Revision A7

5.6 Programming Difference

The W78C438C is programmed in the same way as the W78C32, except that the external data RAM

is accessed by a "MOVX @Ri" instruction. To support address paging, there is an additional 8-bit SFR

"HB" (high byte), which is a nonstandard register, at address 0A1H. During execution of the "MOVX

@Ri" instruction, the contents of HB are output to AP6. The page address is modified by loading the

HB register with a new value before execution of the "MOVX @Ri" instruction. To read/write the HB

register, one can use the "MOV direct" instruction or "read-modify-write" instructions. The HB register

does not support bit-addressable instructions.

[Example]. MOV R1, #0H ; R1 = 0.

MOV 0A1H, #0FFH ; HB contents FFH.

MOVX A, @R1 ; Read the contents of external RAM location FF00H into

; Accumulator.

MOV 0A1H, #12H ; HB contents 12H.

MOVX @R1, A ; Copies the contents of Accumulator into external RAM

; location 1200H.

W78C438C

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6. ELECRICAL CHARACTERISTICS

6.1 Absolute Maximum Ratings

PARAMETER SYMBOL MIN. MAX. UNIT

DC Power Supply

V

DD−VSS

-0.3 +7.0 V

Input Voltage VIN VSS -0.3 VDD +0.3 V

Operating Temperature TOPR 0 70

°C

Storage Temperature TSTG -55 +150

°C

Note: Exposure to conditions beyond those listed under Absolute Maximum Ratings may adversely affect the life and reliability

of the device.

6.2 D.C. Characteristics

(VDD − VSS = 5V ±10%, TA = 25° C, FOSC = 20 MHz, unless otherwise specified.)

PARAMETER SYM. TEST CONDITIONS MIN. TYP. MAX. UNIT

Oper. Voltage VDD 4.5 5 5.5 V

Oper. Current IDD * No load - - 20 mA

Idle Current IIDLE Program idle mode - - 7 mA

Pwdn Current IPWDN Program power-down mode - - 50

µA

Input Leakage

Current

I

LK1

INT2

,

INT3

Internal pull-high

Notes 1, 2

-300 - +10

µA

Input Leakage

Current

I

LK2

RESET

Internal pull-low

Notes 1, 2

-10 - +300

µA

Input Leakage

Current

I

LK3

EA

, Port 0, DP4 Note 1

-10 - +10

µA

Input Leakage

Current

I

LK4 P1, P2, P3, P8 Note 1 -50 - +10

µA

Output Low Voltage VOL1 IOL1 = 2 mA (Port 1, 2, 3, 8) - - 0.45 V

Output High Voltage VOH1

I

OH1 = -100 µA (Port 1, 2, 3, 8)

2.4 - - V

Output Low Voltage VOL2

I

OL2 = 4mA Note 3

(ALE,

PSEN

, P0, DP4)

- - 0.45 V

Output High Voltage VOH2

I

OH2 = -400 µA Note 3

(ALE,

PSEN

, P0, DP4)

2.4 - - V

Output Low Voltage VOL3 IOL2 = 2 mA (AP5, AP6, AP7) - - 0.45 V

Output High Voltage VOH3

I

OH2 = -100 µA (AP5, AP6, AP7)

2.4 - - V

Input Voltage VILT

V

DD = 5V ±10%

0 - 0.8 V

Input Voltage VIHT

V

DD = 5V ±10%

2.4 -

Note 4

V

W78C438C40FL

W78C438C40FL

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